Les principaux objectifs de cette thèse de doctorat ont été de réaliser la synthèse et la caractérisation structurale et dieléctrique des échantillons céramiques ferroélectriques appartenants au système Pb1-xRxZr0,40Ti0,60O3 avec R = Ba et La et x entre 0,00 à 0,50. Ce système a été choisi car il est un matériel ferroélectrique qui a des propriétés physiques intéressantes, comme haute constante diélectrique et piézo-électrique, ce qui les rend candidats potentiels pour des applications telles que les condensateurs à haute densité d'énergie et les actionneurs. Afin d'évaluer le comportement relaxor, les études ont été effectuées avec la variation de la composition, du type de dopage (par des atomes de la même ou différente valence - La ou Ba) et de la taille des particules de céramique, dès l'échelle micrométrique à l'échelle nanométrique. Les échantillons céramiques micrométriques ont été préparées par la méthode de réaction de l'état solide et la frittage dans un four électrique conventionnel. Les données fournies par la technique de diffraction des rayons X de cettes échantillons ont montré une transition de une phase tétragonal pour une phase cubique avec l'augmentation de la concentration de cations substituants. Ces changements ont été attribués à une diminution de distorsion dans le maille cristallographique en raison de l'apparition de défauts causés par l'incorporation de dopage. Les mesures électriques ont été obtenues par spectroscopie d'impédance et ont montré un comportement électrique relaxor à partir de compositions avec plus de 12% at. La et de 30% at. Ba pour les systèmes PLZT et PBZT, respectivement. Les mesures électriques de l'échantillon avec 12%, 13% et 14% at. La et 30% at. Ba présentent un comportement qui, selon la littérature, est liée à une transition de phase spontanée d'un comportement relaxor et au comportement d'un matérial ferroélectrique normal. La technique de diffraction des rayons X a également été utilisé pour surveiller le processus de transition de phase en fonction de la température pour échantillons PLZT et PBZT. Il est possible de voir le changement de structure tétragonal de groupe d'espace P4mm en structure cubique de groupe d'espace Pm-3m. En ce qui concerne la structure locale, nous avons effectué des mesures expérimentales avec la technique de spectroscopie d'absorption des rayons X dans le spectre XANES aux seuils d'absorption de différents éléments pour les échantillons PLZT et PBZT. Dans les cas de seuil d'absorption K du titane, l'intégration de La et Ba atomes de la structure du PZT entraîne une diminution dans le désordre local dans le octaèdre TiO6, vérifié par la réduction du déplacement statique de atome Ti au centre de l'octaèdre TiO6. Cette évolution est plus faible pour les échantillons que montrent le comportement relaxor. Les spectres d'absorption EXAFS au seuil LIII du plomb et seuil K du zirconium ont été effectués aussi et ces mesures indiquent que la structure locale autour des atomes de plomb ou de zirconium est également affectée par l'introduction des atomes de La et Ba dans la structure. Le comportement relaxor a été aussi étudié en fonction de la taille de grain dans une échelle nanométrique. Ainsi les échantillons de compostions PZT, PLZT11 et PBZT10 ont eté préparés en utilisant la méthode de synthèse chimique de polymères précurseurs et le processus de frittage par spark plasma. La caractérisation de ces échantillons par diffraction de rayons X montrent que les paramétres de maille réduisent en comparison avec les échantillons de même composition et taille de grain micrométrique. Pour l'échantillon de composition PLZT11, il est possible de constater le comportement relaxor par les mesures de la constante dieléctrique en fonction de la température. Les changements quand la taille de grain est dans une échelle nanométrique sont attribués à la limitation des frontières de grains, qui provoquent un systéme de tension, responsable de la diminuition des paramétres de maille, et provoquent l'apparition de domaines ferroélectriques nanométriques

A custom-built surface sol-gel pumping system was built for applying conformal sol-gel based coatings with controlled thicknesses on three-dimensional (3-D) nanostructured templates. The 3-D templates utilized in this work were derived from biological species, such as diatoms and butterfly wings, as well as a synthetic photoresist polymer (SU-8). Tin oxide coatings were applied on silica-based diatom frustules using the automated surface sol-gel pumping system. An organic dendrimer method was developed for amplifying hydroxyl groups on the silica-based frustule surfaces to enhance the surface sol-gel deposition process. Conformal tin oxide coatings with controlled thicknesses were obtained on the hydroxyl amplified frustule surfaces; however, little if any deposition was observed on the frustules that were not subjected to the hydroxyl amplification process. The automated surface sol-gel system was also utilized to apply multicomponent tin oxide-doped titania alkoxide chemistries on the wing scales of a blue Morpho butterfly. The alkoxide solutions reacted directly with the OH functionalities provided by the native chitin chemistry of the scales. The tin oxide served as a rutile nucleating agent which allowed the titania to completely crystallize in the high refractive index rutile titania phase with doping concentrations of tin oxide as low as 7 mol % after annealing at 450oC. The tin oxide-doped titania coatings were both nanocrystalline and nanothick and replicated the nanostructured scales with a high degree of precision. Undoped titania coatings applied on the scales required a heat treatment of 900oC to crystallize the coating in the rutile titania phase which led to adverse coarsening effects which destroyed the nanostructed features of the scales. Tin oxide-doped titania coatings were also deposited on 3-D SU-8 photonic crystal structures. The coating was crystallized in an acidic solution at 80oC which led to the formation of rutile titania inverse opal photonic crystal structures which maintained the overall structure and ordering of the template. Barium titanate and europium-doped barium titanate coatings were applied on diatom frustules using a conventional reflux/evaporation deposition process. The silica-based diatom frustules had to first be converted into magnesia/silicon composite replicas using a gas/solid displacement reaction to render the template chemically compatible with the barium titanate-based coating. Conformal titanate-based coatings were obtained on the magnesia frustule replicas possessing uncontrolled thicknesses and excess inorganic particles using the reflux/evaporation deposition process. The europium-doped barium titanate coated frustules exhibited bright red photoluminescent properties upon stimulation with an ultraviolet light source.

Actuellement, les céramiques diélectriques suscitent de nombreux travaux pour des applications microondes (résonateurs diélectriques accordables ou déphaseurs). Pour cela, elles devront être commandables - modification de la constante diélectrique sous l'action d'un champ électrique – avoir une permittivité modérée (de 30 à 1000) et des tangentes de pertes les plus faibles possibles. Dans ce but, nous avons étudié des céramiques composites à base de Ba0.6Sr0.4TiO3 (BSTO) et d'un oxyde non-ferroélectrique de faible permittivité (MgTiO3 ou MgO). Il s'agissait de corréler la microstructure des céramiques et leurs propriétés diélectriques, notamment la température de Curie et les relaxations diélectriques.<br />Des céramiques à grains nanométriques de BSTO, pour comparaison à des céramiques à grains microniques obtenues par frittage conventionnel, ont été réalisées par pressage à chaud de poudres broyées par attrition. L'hypothèse que ces céramiques amélioreraient les performances des dispositifs microondes s'est avérée inexacte. Une réduction des permittivités est observée mais au détriment de la commandabilité et des pertes. Les céramiques à grains micrométriques de BSTO dopées Mn ont conduit aux meilleures performances. Cependant, les pertes mesurées atteindraient une valeur limite basse lors de l'optimisation du matériau ; il s'agirait de pertes intrinsèques au matériau dues à une relaxation diélectrique de type dipolaire dans la gamme des GHz. Il faudra le vérifier par des mesures en infra-rouge.<br />Les températures de Curie (Tc) chutent drastiquement lors de l'ajout de MgTiO3 ou MgO, montrant une réaction entre les oxydes - observée par DRX seulement pour les céramiques à base de MgTiO3. Une faible interdiffusion abaisse donc largement Tc, et de ce fait la permittivité, et dégrade la commandabilité. Pour pallier ces problèmes, une structure multicouche est testée. Un affinement des dopages des composites pourrait aussi améliorer les performances.

[pt] Nanofolhas de ferrititanato com estrutura tipo lepidocrocita foram sintetizadas a partir de um precursor de baixo custo (areia ilmenítica), via rota hidrotérmica alcalina. Dois tipos de nanofolhas com alto e baixo teor de sódio foram obtidos: a) nanofolhas sódicas (NaLTs) e b) nanofolhas protonizadas (pLTs), obtidas mediante uma reação rápida de troca-ácida à temperatura ambiente. As capacidades de troca catiônica de ambos os tipos de nanofolhas foram determinadas seguindo-se a norma C 837 da ASTM. Após a síntese desses dois nanomateriais com diferentes teores de sódio foi estudado o processo de esfoliação em camadas de espessura sub-nanométrica, sob agitação intensa à temperatura de 60 C, utilizando-se como o agente de esfoliação pela primeira vez numa estrutura lepidocrocítica o sal cloreto de dimetildioctadecilamônio (2C18), visando a posterior aplicação das nanofolhas esfoliadas como reforço em nanocompósitos de matriz polimérica. O intuito de aplicar estes reforços em uma matriz polimérica foi buscar uma dispersão mais homogênea das folhas esfoliadas, além do aumento da compatibilidade das nanocargas com a matriz polimérica pela presença dos grupos orgânicos do sal quimicamente ligados às nanofolhas e, consequentemente, o incremento das propriedades térmicas e mecânicas do material polimérico. Dependendo do teor de sódio, foram obtidas nanofolhas esfoliadas e/ou intercaladas que foram posteriormente caracterizadas por fotometria de chama, espetroscopia de infravermelho, área superficial específica por adsorção de N2, termogravimetria, difração de raios-X de alto ângulo, espalhamento de raios-X a baixo ângulo, microscopia de força atômica e microscopia eletrônica de transmissão. Para a fabricação dos nanocompósitos foram utilizadas duas matrizes: a) uma de PEAD puro e b) a outra de PEAD com adição de uma porcentagem baixa, e constante, de polietileno funcionalizado com anidrido maleico (PE-g-MA), sendo reforçadas com as nanocargas protonizadas virgens (pLTs) e esfoliadas (pLTs-o-2C18) nas concentrações de 1,0; 2,0 e 4,0 por cento p. Finalmente, foram avaliadas as propriedades mecânicas e térmicas dos nanocompósitos por meio de ensaios de tração, termogravimetria, calorimetria diferencial de varredura e dilatometria. Os nanocompósitos preparados com pLTs virgem e os fabricados com a adição de agente de acoplamento de PE-g-MA apresentaram um aumento no módulo de Young de aproximadamente 12,8 por cento e 5,1 por cento para cargas de 4 por cento e 2 por cento em peso de pLTs virgem, respectivamente. Os nanocompósitos, que apresentam o maior aumento no limite de escoamento foram os reforçados com 4 por cento p de nanofolhas esfoliada (pLTs-o-2C18). No entanto, estes materiais apresentam uma diminuição no módulo de Young de aproximadamente 12 por cento. Os nanocompósitos com o maior aumento no módulo de Young foram os preparados com 4 por cento p pLTs ( aproximadamente 12,8 por cento), enquanto sua tensão no escoamento também foi melhorada (um aumento de aproximadamente 4 por cento). A incorporação de nanofolhas não afetou significativamente as propriedades de estabilidade térmica da matriz e uma diminuição no coeficiente de expansão térmica de 4 a 5,5 por cento foi apenas observada para nanocompósitos preparados com pLTs virgens. O grau de cristalinidade diminuiu para todos os nanocompósitos fabricados, no qual variou de 2,17 até 26 por cento. / [en] Ferrititanate nanosheets with lepidocrocite-like structure were synthesized from a low cost precursor (ilmenite sand) through alkaline hydrothermal route. Two types of nanosheets with high and low-sodium content were obtained: a) sodium rich nanosheets (NaLTs) and b) protonated nanosheets (pLTs), obtained by a rapid acid-exchange reaction at room temperature. The cation exchange capacities of both types of nanosheets were determinated according ASTM C 837. After the synthesis of these two nanomaterials with different sodium levels, it was studied the exfoliation process to obtain monolayers of nanometric lateral dimensions under intensive stirring at 60 C, using dimethyldioctadecylammonium cloride (2C18) as the exfoliating agent of the lepidocrocite-like ferrititanate nanosheets for the first time, aiming the further application of the exfoliated nanosheets as reinforcement in polymer matrix nanocomposites. The purpose of the addition of these nanofillers within a polymer matrix is to obtain a more homogeneous dispersion of exfoliated nanosheets, as well as the improvement of the compatibility between nanofillers and the polymer matrix, due to the presence of the organic groups from 2C18, chemically attached to nanosheets and hence, to promote the an increase on mechanical and thermal properties of the polymeric matrix. Depending on the sodium content, it was obtained exfoliated and/or intercalated nanosheets that were further characterized by flame photometry, infrared spectroscopy, specific surface area by N2 adsorption, thermogravimetry, X-ray powder diffraction (XRPD) and of small angle X-ray scattering (SAXS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). For the manufacturing of nanocomposites two types of matrices were used: a) neat high density polyethylene (HDPE) and b) HDPE with the addition of a low percentage of polyethylene-graft-maleic anhydride (PE-g-MA). Pristine nanosheets (pLTs) and exfoliated nanosheets (pLTs-O-2C18) were used as nanofillers at loadings of 1.0; 2.0 and 4.0 wt percent. Finally, we assessed the mechanical and thermal properties of the as-prepared nanocomposites through tensile tests, thermogravimetry analysis (TGA), differential scanning calorimetry (DSC) and dilatometry. Nanocomposites prepared with pristine pLTs and those manufactured with the addition of PE-g-MA coupling agent showed an increase on the Young modulus of about 12,8 percent and 5,1 percent for loadings of 4wt percent and 2 wt percent of pristine pLTs, respectively. The nanocomposites that present the highest increase on yield stress were reinforced with 4 wt percent of exfoliated nanosheets (pLTs-o-2C18). However, these materials presents a decrease in the Young modulus of about 12 percent. The nanocomposites with the highest increase on Young Modulus were those prepared with 4 wt percent of pristine ( about 12,8 percent), and the yield stress was also improved (increase of about 4 percent). The incorporation of nanosheets did not affect significantly the thermal stability properties of the matrix and a decrease on the coefficient of thermal expansion was solely observed for nanocomposites prepared with pristine pLTs. The degree of crystallinity decreased for all the manufactured nanocomposites, in the range of about 2,17 t-26 percent for nanocomposites prepared with pristine pLTs and those fabricated with the addition of PE-g-MA, respectively. up to about pLTs with the addition of PE-g-MA.

The word piezo in greek means \to compress". Piezoelectric sensors work on the principle of direct piezoelectric effect, where a mechanical input generates a corresponding electric charge. The advantages of these sensors are wide fre-quency range of operation, high stiffness and small size. The main limitation of a piezoelectric sensor is that it cannot be used in measurements that are truly static. When a piezoelectric sensor is subjected to a static force, a fixed amount of charge is developed which would eventually decay at a rate dependent on the external impedance of the sensor circuitry. Operating sensors at resonance have been one of the methods to overcome the limitation of using piezoelectric sensors for static measurements. However, since both actuation and sensing are done by the same piezoelectric element, this results in a cross-talk of input and output signals. The drawback of using single piezoelectric element for actuation and sensing is overcome in this work by using two identical elements|one for actuation and one for sensing. The operating frequency is about 10 % of the natural frequency of the sensor, thus enabling to operate the sensor in non resonant mode. Since the actuation and sensing mechanisms are separated, static measurement can be carried out. The output signal from the sensing element is monitored by a Lock-in amplifier which works on the principle of phase sensitive detection. The advantage of this sensor design is high sensitivity along with narrow band detection. It can be shown that the voltage output of the sensor Vout / a1 + m(b1 + b2F + b3K) + c1F + d1K, where m and K are the external mass and interaction stiffness, respectively, F is the force acting on it. By maintaining any two of these three quantities constant, the remaining one can be measured without any difficulty. The non resonant mode of operation makes it possible to explore the potential of this sensor in investigating mechanics of solid-liquid (viscous), solid-solid (inelastic) and solid-tissue(viscoelastic) interactions. High sensitivity, wide range of measurement (1 g{1 g) and high resolutio(0.1 g) of the non resonant mass sensor makes it possible to use it in measure-ment of very small masses of the order 1 g. Typically, resonant sensors such as quartz crystal microbalance (QCM) are used for mass measurements at that range. However, since the performance of resonant sensors is controlled by damp-ing, a phenomenon known as `missing mass effect' arises. Operating a sensor in non resonant mode (stiffness controlled mode) is a way to overcome this problem, especially when the mass is viscous and/or viscoelastic in nature. Drosophila fly, egg and larvae are the viscoelastic masses that are measured using this non res-onant sensor. Evaporating sessile drops of water and Cetyl trimethylammonium bromide (CTAB) surfactant solution from nominally flat surfaces are monitored to characterize the sensor for viscous mass measurement. Evaporation rate per unit surface area remains more or less constant, during the initial stages of evap-oration. When the surfactant concentration is varied, evaporation rate per unit surface area is highest for solutions around critical miscelle concentration (CMC). A study is carried out to understand the effect of concentrations on spreading of ink over inkjet printing paper. It is found that the spreading is least around CMC, since spreading is dependent on the rate of evaporation. The non resonant piezoelectric sensor which has high stiffness and quick re-sponse is also capable of measuring very small frictional forces. This sensor is configured to work as an inertial slider. Friction measurement at micro scales is important for designing microsystems such as stick-slip actuators. At such length scales, experiments have to performed at low loads and high excitation frequencies. The support stiffness of such systems should be high and the force of friction generated during slipping, when displacements are smaller than the contact radius, are of the order of few N. The displacement during slipping (S) is dependent on the amplitude of the input voltage to the actuation element. The frictional force measured during slipping by the sensor element indicates that the co-efficient of friction ( ) is independent of the sliding velocity. The developed non resonant sensor in this work under small amplitude exci-tation, can measure force gradient (i.e. stiffness). The total force generated when a needle is inserted into a viscoelastic material is a sum of force due to stiffness of the material, friction and the cutting force at the tip. The force due to stiffness is dominant when the needle is bending the tissue before the puncture occurs. Use of the non resonant sensor in tandem with strain gauge force sensor enables distinguishing the three components of the total force. The slope of the force-displacement (F -d) curve during the initial stages of needle penetration into the viscoelastic material, before puncture, is indicative of the stiffness of the mate-rial. The peak force measured during penetration is higher for needles with larger diameters and lower insertion velocities. The viscoelastic response (relaxation) of the material remains independent of the insertion velocity, for a given thickness of the material and a constant needle diameter. In summary, the sensor designed and developed in this work operates in stiffness controlled mode to eliminate the `missing mass effect' encountered dur-ing resonant mode of operation, has been clearly highlighted. Mass, force and stiffness measurements are possible over a wide range just by varying the ampli-tude of the input signal to the actuator element. The advantages such as high stiffness, small size and high response makes it advantageous to carry out in-situ micro scale studies in scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Os materiais ferroelétricos têm sido utilizados em muitas áreas da tecnologia e da ciência, pois possuem um grande número de aplicações, como: sensores; transdutores; capacitores; dispositivos ópticos; dentre outras. A busca por novos materiais cerâmicos ferroelétricos tem sido grande. Um dos materiais cerâmicos ferroelétricos mais estudados é o titanato de bário (BT). São vários os métodos de produção e caracterização do titanato de bário. Neste trabalho, pós cerâmicos de titanato de bário foram obtidos por reação do estado sólido a partir de misturas reacionais calcinadas em diferentes temperaturas entre 400C e 900C. Foram três as misturas reacionais: não dopadas; dopadas com 1%; e dopadas com 5% de dióxido de cério (CeO2). A identificação da formação do BT, nos pós cerâmicos produzidos, foi feita a partir de três técnicas de caracterização: difração de raios X (DRX); espectroscopia fotoacústica (PAS); e técnicas de análise térmica. Com a técnica DRX, difratogramas mostraram que a plena formação do titanato de bário ocorreu a partir da temperatura de calcinação de 700C. Para a amostra não dopada com cério e calcinada a 800C, houve deslocamento de todos os picos de difração. Nas amostras dopadas com dióxido de cério houve deslocamento de todos os picos de difração, em relação as amostras não dopadas. Observou-se também que nas amostras dopadas com 5% de CeO2, e calcinadas a 700C e 800C, resíduos de dióxido de cério foram observados nos difratogramas. Com a técnica PAS, espectros de absorção foram obtidos. Foi possível observar uma grande diferença de absorção da amostra calcinada a 600 e 630C, indicando a formação do titanato de bário a partir da temperatura de 630&#61616;C, nas amostras sem a dopagem dióxido de cério. Houve um alargamento nas bandas de absorção a partir da temperatura de 600C, quando o dióxido de cério entrou na matriz. Foi também possível determinar as energias de band-gap das amostras utilizando o método de Tauc. Com as técnicas de análise térmica, em especial através da técnica termogravimétrica (TG/DTG), foi comprovado que até 400C não havia formação de titanato de bário. Visto que nesta temperatura de calcinação houve a maior perda de massa durante a rampa de aquecimento. O início da formação do titanato de bário foi observado a partir da temperatura de calcinação de 500C, assim como nas técnicas DRX e PAS. Portanto, com os resultados apresentados, foi demonstrada a identificação da formação do titanato de bário nas misturas reacionais calcinadas, com auxílio das potencialidades das três técnicas utilizadas. / Ferroelectric materials have been used in many areas of technology and science, because they have a large number of applications, such as sensors; transducers; capacitors; optical devices; among others. The search for new ferroelectric ceramics has been great. One of the most studied ferroelectric ceramic material is barium titanate (BT). There are several methods for production and characterization of barium titanate. In this work, ceramic powders of barium titanate were obtained by solid state reaction from reaction mixtures calcined at different temperatures between 400C and 900C. Three reaction mixtures were used: undoped; doped with 1%; and 5% doped with cerium dioxide (CeO2). The identification of the formation of BT, for the ceramic powders produced, was taken from three characterization techniques: X-ray diffraction (XRD); photoacoustic spectroscopy (PAS); and thermal analysis techniques. With the technique XRD diffraction patterns showed that complete formation of the barium titanate occurred after the calcination temperature of 700C. For the sample not doped with cerium and calcined at 800C, there was displacement of all diffraction peaks. In samples doped with cerium dioxide was no displacement of all diffraction peaks, comparing to undoped samples. It was also observed that the samples doped with 5% CeO2 and calcined at 700C and 800C, cerium dioxide residues were observed in the diffraction pattern. The absorption spectra were obtained with the technique PAS. It was possible to observe a large difference in absorption spectra in the samples calcined at 600C and 630C, indicating the formation of barium titanate at temperature of 630C in the samples without doping of cerium dioxide. There was an enlargement in the absorption band above temperature of 600C when the cerium dioxide was introduced into the matrix. It was also possible to determine the band-gap energy of the samples using the method of TAUC. With thermal analysis techniques, in particular by thermogravimetric technique (TG/DTG), has been proven that up to 400C there was no formation of barium titanate. Once, in this calcination temperature there was the largest mass loss during the heating ramp. The onset of formation of barium titanate was observed from the calcination temperature of 500C, as it has been found by the XRD and PAS techniques. Therefore, with the results presented, the identification of the formation of barium titanate calcined in reaction mixtures with the aid of the potentialities of the three techniques was demonstrated.

Orientador: Prof. Dr. Wendel Andrade Alves / Tese (doutorado) - Universidade Federal do ABC. Programa de Pós-Graduação em Ciência e Tecnologia/Química, 2016. / Nanotubos de titanato tem atraído muita atenção devido a suas propriedades únicas, que permitem sua aplicação em catálise, fotocatálise, e no desenvolvimento de dispositivos de conversão de energia. No entanto, esses materiais são capazes de absorver somente radiação UV, o que torna necessária sua sensibilização frente à radiação visível que pode ser feito através da dopagem ou sensibilização com corantes. Neste trabalho, nanotubos de titanato foram preparados através da síntese hidrotérmica alcalina e dopados usando um método de troca iônica seguida por uma etapa de calcinação a 200 ºC e 400 ºC, resultando em duas séries de catalisadores: nanotubos de titanato dopados com nitrogênio (NTiNTs) e nanotubos de dióxido de titânio dopados com nitrogênio (NTiO2NTs), respectivamente. A caracterização destes materiais revelou que a temperatura de calcinação afeta a intensidade de cor, área superficial, energia band gap e natureza da espécie de nitrogênio dopante. Os catalisadores NTiO2NTs reúnem as propriedades que os qualificam como melhores fotocatalisadores, sendo capazes de degradar de 1,8% (m/m, massa de corante degradado por 100g de catalisador) a 2,9%, enquanto os NTiNTs foram capazes de degradar somente de 0,17%mg mg-1 a 0,60%. Os catalisadores NTiNTs e NTiO2NTs também foram sensibilizados com ftalocianina de cobre(II) tetracarboxilada. Observou-se que a sensibilização não afeta a forma nem a estrutura cristalina dos nanotubos, no entanto, ela promove alterações nas propriedades superficiais levando a interações diferenciadas entre os tubos. Esses materiais foram aplicados na degradação de rodamina B através de mecanismos de fotocatálise e catálise mediada por H2O2. Observou-se que os catalisadores sensibilizados apresentam eficiência fotocatalítica cerca de 50% menor do que os materiais não sensibilizados. No caso da catálise mediada por H2O2 a sensibilização aumenta a atividade catalítica, podendo atingir 100% de eficiência. Por fim, foram desenvolvidos novos eletrodos multi-hierárquicos baseados em filmes de nanobastões de óxido de zinco (ZnONR) decorados com nanotubos de titanato, utilizando glicina como uma ponte para promover o aumento da interação entre as estruturas. Estes eletrodos foram aplicados como fotoanodos no desproporcionamento fotoeletroquímica da água, gerando O2 e H2. Os resultados mostraram que a heterojunção dos dois óxidos metálicos leva a um aumento da eficiência fotoeletroquímica. Desse modo, os eletrodos multihierárquicos são capazes de produzir correntes de geração de O2 de 0,90 mA cm-2 (a 1,23 V vs ERHE), enquanto os eletrodos de ZnONR puros produzem 0,45 mA cm-2. O potencial de evolução de O2 também diminui de 0,8 V (vs ERHE) para eletrodos de TiNTs para 0 V no caso dos eletrodos multi-hierárquicos. / Titanate nanotubes have attracted much attention due do their unique properties which allow their application in catalysis, photocatalysis and energy conversion devices development. However, this material is able to absorb only UV radiation making necessary its sensibilization toward visible radiation that can be done through doping or dye sensibilization. In this work, titanate nanotubes were prepared through alkaline hydrothermal synthesis and doped using an ion exchange methodology followed by a calcination step at 200 ºC and 400ºC, resulting in two series of catalysts: nitrogen doped titanate nanotubes (NTiNTs) and nitrogen doped titanium dioxide nanotubes (NTiO2NTs), respectively. The characterization of these materials revealed that the calcination temperature affects color intensity, surface area, band gap energy and nature of doping nitrogen species. The NTiO2NTs catalysts gather the properties that qualify them as better photocatalysts, being capable of degrading from 1,8% (m/m, degraded dye mass by 100 g of catalyst) to 2,9%, whereas the NTiNTs are capable of degrading only 0,17% to 0,60%. The catalysts NTiNTs and NTiO2NTs were also sensitized with tetracarboxylate cooper(II) phthalocyanine. It has been observed that the sensibilization does not affect the morphology or crystalline structure of the nanotubes; however, it promotes changes on the surface properties leading to differentiated interactions between the tubes. These materials were applied on rhodamine B degradation through mechanisms of photocatalysis and catalysis mediated by H2O2. It was observed that the sensibilized catalysts exhibit photocatalytic efficiency of about 50% lower than nonsenbilized materials. In the case of catalysis mediated by H2O2 the sensibilization increases catalytic activity, which can reach 100% of efficiency. Finally, new multihierarchical electrodes were developed, based on zinc oxide nanorods (ZnONR) films decorated with titanate nanotubes, using glycine as a bridge to promote the increasing of the interaction between the structures. These electrodes were applied as photoanodes for photoelectrochemical water splitting, producing O2 e H2. The results show that the heterojunction of the two metal oxides leads to an increasing of the photoelectrochemical efficiency. Thus, the multi-hierarchical electrodes are capable of producing O2 evolution currents of 0.90 mA cm-2 (at 1.23 V vs ERHE), whereas the pure ZnONR electrodes produce 0.45 mA cm-2. The O2 evolution potential also decreases from 0.8 V (vs ERHE) for TiNTs electrodes to 0V for the multi-hierarchical electrodes.

Non-centrosymmetric materials that can be polarized under applied mechanical stress or electric field are piezoelectric in nature and the phenomenon is called piezoelectric effect. They are broadly classified as direct and converse piezoelectric effects. Piezo-ceramics have a wide range of applications such as piezoelectric actuators, sensors, and transducers. Among piezoceramics, ferroelectric based materials are imperative owing to the existence of spontaneous polarization in these systems. Several materials are investigated starting from naturally occurring crystals to synthetic ceramics but are limited in their application range. The piezoelectric and ferroelectrics properties of the solid-solutions based on lead zirconate and lead titanate called lead zirconate titanate (PZT), lead magnesium niobate-lead titanate (PMN-PT), lead zinc niobate-lead titanate (PZN-PT) (near morphotrophic phase boundary (MPB)) demonstrate their potential for myriad device applications besides inciting a great deal of academic interest. They have been widely used for commercial applications such as ultra sound transducers, ultrasonic motors, fuel injector actuators, nano positioners in scanning electron microscope etc. However, these materials contain more than 60% lead by weight and volatization of Pb at higher temperature, and disposal of lead results in environmental pollution and are fatal to human health. This gave an insight to search for lead-free solid solutions covering a wide spectrum of applications akin to that of PZT. The search for alternatives to lead based piezoelectric materials is now being focused on modified barium titanates and alkali niobates in which the incidence of MPB was reported similar to that of PZT. In this thesis the results pertaining to the various investigations carried out on modified barium titanates, Ba(Zr0.2Ti0.8)O3- x(Ba0.7Ca0.3)TiO3(BCZT), and alkali niobates, potassium sodium niobate (KNN), are presented. Especially, lead-free piezoelectric material Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3(BCZT) with x= 0.5 has attracted great attention due to its excellent piezoelectric properties. Contrary to the other Pb-free systems, the BZT–BCT phase diagram shows a Morphotropic Phase Boundary (MPB) characterized by the existence of a tri-critical point (TCP), which is also the case for PZT and PMN–PT. One drawback of the BZT–xBCT (x=0.5) is its high sintering temperature (where it exhibits the largest d33 of 550 – 620pC/N). Several methods have been adopted and various additives are being added to bring down the sintering temperature, since high d33 requires an optimized sintering temperature of around 1540oC which also shows excellent ferroelectric properties. However, the methods that were reported in the literature to synthesize the above materials do not guarantee compositional homogeneity and also there is a limitation in obtaining ceramics of enhanced grain size as the ceramics comprising larger grains are demonstrated to exhibit high piezoelectric coefficients. Therefore to address these issues, the simple soft chemical route was adopted to synthesize chemically homogenous powder and the influence of microstructure (grain size) and ferroelectric domains on piezoelectric properties of the BCZT at nano and micron sized crystallites was studied. The results obtained are classified into chapter 3 and chapter 4 accordingly apart from introduction, materials, and methods. Another challenging area of research in lead free piezoceramics for nanoscale device application is to synthesize materials and to visualize the piezoelectric properties at nanoscale with controlled shapes and sizes. For that, Mg2+ ion was chosen as the dopant especially on Ba2+ sites to synthesize Ba0.95Mg0.05Zr0.1Ti0.9O3 (BMZT) nanocrystals, as MgO is known to be an effective grain growth inhibitor in many functional and structural ceramics. Therefore in the present thesis Mg2+ ion was chosen to exercise a strict control over the grain size. The results obtained from this title compound are discussed in chapter 5. Another class of material is K0.5Na0.5NbO3 (KNN), which has been considered a good candidate for lead-free piezoelectric materials. KNN exhibits an MPB around 50% K and 50% Na separating two orthorhombic phases from the complete solid solution of NaNbO3 (Anti-ferroelectric) and KNbO3 (ferroelectric). The major problem associated with KNN ceramic is its complex densification process; difficulty in processing and volatilization of sodium at higher sintering temperature leading to stoichiometric discrepancy. To overcome these difficulties, in the present investigations, an attempt has been made to fabricate KNN ceramics by employing the liquid phase sintering method. In this chapter, B2O3 and borate based glass (0.5 Li2O - 0.5K2O- 2B2O3) were chosen to improve the densification, grain size and their effects on the physical properties of the KNN ceramics are discussed in chapter 6. In chapter 7, KNN crystallites (with size varying from nano to micrometers) were dispersed in the Polyvinylidene fluoride (PVDF) matrix to obtain a polymer/nano or micro crystal composites and the effect of nano and micron sized KNN fillers on the structural, dielectric and piezoelectric properties were investigated. The results obtained pertaining to these aforementioned investigations are organized as follows. In Chapter 1, a brief introduction to the field of ferroelectricity, piezoelectricity, and piezoelectric materials. The emphasis has been on the ferroelectric based piezoelectric materials belonging to the perovskite family of oxides. A brief exposure to the conventional lead based piezoceramics, lead zirconate titanate (PZT) is discussed. Furthermore, drawbacks associated with lead based ceramics are highlighted and alternatives to PZT based ceramics such as modified barium titanate and alkali niobate solid solutions are focused, leading to the motivation and objectives of our work. Chapter 2 describes the various experimental techniques that are employed to synthesize and characterize the materials under investigation. Chapter 3 deals with details concerning the characterization of Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) nanocrystals prepared via complex oxalate precursor route at a relatively low temperature (800°C/5h). The phase formation temperature of BCZT at nanoscale was confirmed by thermogravimetric (TG), differential thermal analysis (DTA) followed by X-ray powder diffraction (XRD) studies. Fourier Transform Infrared (FTIR) spectroscopy was carried out to confirm the complete decomposition of oxalate precursor into BCZT phase. The XRD and profile fitting revealed the coexistence of cubic and tetragonal phases and was also corroborated by Raman study. Transmission electron microscopy (TEM) studies carried out at 800°C and 1000°C/5h heat treated BCZT powder revealed the crystallite size to be in the range of 20 – 50 nm and 40 – 200 nm respectively. The optical band gap for BCZT nanocrystalline powder was obtained using Kubelka Munk function and was found to be around 3.12 ± 0.02 eV and 3.03± 0.02 eV respectively for 800°C (20 – 50 nm) and 1000°C/5h (40 – 200 nm) heat treated samples. The piezoelectric properties were studied for two different crystallite sizes (30 and 70 nm) using piezoresponse force microscope (PFM). The d33 coefficients obtained for 30 nm and 70 nm sized crystallites were 4 pm/V and 47 pm/V respectively. These were superior to those of BaTiO3 nanocrystal (≈ 50 nm) and promising from the technological/industrial applications perspective. Chapter 4 deals with the studies concerning the effect of microstructure (Grain size) and ferroelectric domains on physical properties of Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics. Fine powders comprising nanocrystallites of Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) were synthesized via oxalate precursor method which facilitated to obtain homogenous and large grain sized ceramics at a lower sintering temperature. The compacted powders were sintered at various temperatures in the range of 1200°C - 1500°C for an optimized duration of 10h. Interestingly the one that was sintered at 1450°C/10h exhibited well resolved Morphotrophic Phase Boundary (MPB). The average grain size associated with this sample was 30 µm accompanied by higher domain density mostly with 90° twinning. These were believed to make a significant contribution towards obtaining large strain of about 0.2 % and piezoelectric coefficient as high as 563 pC/N. The maximum force that was generated by BCZT ceramic (having 30 µm grain size) was found to be 161 MPa which is much higher than that of known actuator materials such as PZT (40 MPa) and NKN-5-LT (7 MPa). Chapter 5 reports the details involving the synthesis, structural, optical, and piezoelectric response of lead free Ba0.95Mg0.05Zr0.1Ti0.9O3 nanocrystalline powder. Nanocrystalline powders of Ba1-xMgxZr0.1Ti0.9O3 (x=0.025 - 0.1) were synthesized via citrate assisted sol-gel method. Interestingly, the one with x=0.05 in the system Ba1-xMgxZr0.1Ti0.9O3 exhibited fairly good piezoelectric response apart from the other physical properties. The phase and structural confirmation of synthesized powder was established by X-ray powder diffraction (XRD) and Raman Spectroscopic techniques. Two distinct Raman bands i.e., 303 cm-1 and 723 cm-1 characteristic of the tetragonal phase were observed. Thermogravimetric analysis (TGA) was performed to evaluate the phase decomposition of the as-synthesized Ba0.95Mg0.05Zr0.1Ti0.9O3 sample as a function of temperature. The average crystallite size associated with Ba0.95Mg0.05Zr0.1Ti0.9O3 was calculated using Scherrer formula based on the XRD data and was found to be 25 nm. However, Scanning and Transmission Electron Microscopy studies revealed the average crystallite size to be in the range of 30-40 nm. Kubelka-Munk function was employed to determine the optical band gap of these nanocrystallites. The piezoelectric response of 26 pm/V was observed for Ba0.95Mg0.05Zr0.1Ti0.9O3 nanocrystal by Piezoresponse Force Microscopy (PFM) technique. Photoluminescence (PL) study carried out on these nanocrystals exhibited a blue emission (470 nm) at room temperature. Chapter 6 describes the effect of the addition of B2O3 on the density, microstructure, dielectric, piezoelectric and ferroelectric properties of K0.5Na0.5NbO3 ceramics. Boron oxide (B2O3) addition to pre-reacted K0.5Na0.5NbO3 (KNN) powders facilitated swift densification at relatively low sintering temperatures which was believed to be a key to minimize potassium and sodium loss. The base KNN powder was synthesized via solid-state reaction route. The different amounts (0.1 to 1 wt %) of B2O3 were added, and ceramics were sintered at different temperatures and durations to optimize the amount of B2O3 needed to obtain KNN pellets with the highest possible density and grain size. The 0.1 wt% B2O3 added KNN ceramics sintered at 1100°C for 7h exhibited higher density (98%) with grain size of ~5 µm. Scanning electron microscopy (SEM) studies confirmed an increase in average grain size with increasing B2O3 content at the appropriate temperature of sintering and duration. The B2O3 added KNN ceramics exhibited improved dielectric and piezoelectric properties at room temperature. For instance, 0.1 wt% B2O3 added KNN ceramic exhibited d33 value of 116 pC/N which is much higher than that of pure KNN ceramics. Interestingly, all the B2O3 added (0.1 to 1wt %) KNN ceramics exhibited polarization – electric field (P vs E) hysteresis loops at room temperature. The remnant polarization (Pr) and coercive field (Ec) values are dependent on the B2O3 content and crystallite size. The details pertaining to the effect of the addition of borate based glass (0.5 Li2O - 0.5K2O- 2B2O3) on the physical properties of K0.5Na0.5NbO3 ceramics are also reported in this chapter. The addition of powdered 0.5 Li2O - 0.5K2O- 2B2O3 (LKBO) glass (0.5 to 2 wt%) to potassium sodium niobate, K0.5Na0.5NbO3 (KNN) powder facilitated higher densification which resulted in improved physical properties that include dielectric, piezoelectric and ferroelectric. The required polycrystalline powders of KNN were synthesized through solid-state reaction route, while LKBO glass was obtained via the conventional melt-quenching technique. Pulverized glass was added to KNN powders in different wt% and compacted at room temperature and these were sintered around 1100°C. Indeed the addition of optimum amount (1 wt %) of LKBO glass to KNN ceramics facilitated lowering of sintering temperature accompanied by larger grains (8 µm) with improved density. The dielectric constant (εr) measured at room temperature was 475 (at 10 kHz), whereas it was only 199 for the LKBO glass free KNN. The piezoelectric coefficient (d33) was found to be 130 pC/N for 1wt% LKBO added glass, which was much higher than that of pure KNN ceramics (85 pC/N). Indeed, the LKBO glass added samples did exhibit well saturated P versus E hysteresis loops at room temperature. Though there was no particular trend observed in the variation of Pr with the increase in glass content, the Pr values were higher than those obtained for KNN ceramics. The improved physical properties of KNN ceramics encountered in these studies were primarily attributed to enhancement in density and grain size. Chapter 7 presents a comparative study on the structural, dielectric and piezoelectric properties of nano and micron sized K0.5Na0.5NbO3 fillers in PVDF composites. Polymer nanocrystal composites were fabricated by embedding polyvinylidene fluoride (PVDF) with different vol% of K0.5Na0.5NbO3 (KNN) nanocrystallites using hot-pressing technique. For comparison, PVDF-KNN microcrystal composites of the same compositions were also fabricated which facilitated the crystallite size (wide range) effect studies on the dielectric and piezoelectric properties. The structural, morphological, dielectric, and piezoelectric properties of these nano and micro crystal composites were investigated. The incorporation of KNN fillers in PVDF at both nano and micrometer scale above 10vol% resulted in the formation of polar β-form of PVDF. The room temperature dielectric constant as high as 3273 at 100Hz was obtained for PVDF comprising 40 vol% KNN nanocrystallites due to dipole –dipole interactions (as the presence of β-PVDF is prominent), whereas it was only 236 for PVDF containing the same amount (40 vol%) of micron sized crystallites of KNN at the same frequency. Various theoretical models were employed to predict the dielectric constants of the PVDF-KNN nano and microcrystal composites. PVDF comprising 70 vol% micronmeter sized crystallites of KNN exhibited d33 value of 35pC/N, while the nanocrystal composites of PVDF-KNN did not exhibit any piezoelectric response perhaps due to unrelieved internal stress within each grain besides having less number of domain walls. The Thesis ends with summary and conclusions, though each chapter is provided with conclusions and a complete list of references.

Neste trabalho, eletrocerâmicas a base de BaTiO3 e Ba(1-x)Erx TiO3 com x(Er3+) = 0,001, 0,010 e 0,050 foram preparadas através do método dos precursores poliméricos, com o propósito de estudar as possíveis relações entre os comportamentos termistor (tipo PTCR) e varistor em nível elétrico e microestrutural. Após calcinação dos pós-precursores em 700°C por 2h, os pós compactados isostaticamente a 300 MPa na forma de pastilhas, foram sinterizados em 1200°C, 1250°C, 1300°C e 1350°C. Foram realizadas caracterizações estruturais e microestruturais aplicando as técnicas de difração de raios X e microscopia eletrônica de varredura por emissão de campo, além de estudos elétricos e dielétricos utilizando a técnica de espectroscopia de impedância como ferramenta principal. Destas caracterizações, verificou-se a obtenção de materiais cerâmicos densos e com valores médios de tamanhos de grãos dependentes de x(Er3+) bem como da temperatura de sinterização. A análise dos resultados de espectroscopia de impedância via circuito equivalente revelaram para as amostras de Ba(1-x)ErxTiO3 que as respostas elétricas podem ser associadas a 3 microrregiões (Modelo Core-Shell): os núcleos e as \"couraças\", ambas relacionadas as porções internas dos grãos cerâmicos, mais os contornos de grãos, respectivamente. Considerando as contribuições resistivas associadas a cada microrregião, em função das tensões e temperaturas aplicadas, os comportamentos varistor e termistor das eletrocerâmicas de Ba(1-x)ErxTiO3 são apresentados e caracterizados em relação ao comportamento das amostras de BaTiO3. No âmbito geral, este trabalho revela uma boa correlação entre estes fenômenos e suas associações a cada microrregião identificada pelos modelos de circuitos equivalentes supostos na literatura. / Electroceramics based on Ba(1-x)ErxTiO3, with x(Er3+) = 0,001, 0,010, 0,050 stoichiometry were synthesized by the polymeric precursors method in an attempt to correlate the possible relations between the PTCR effect and the varistor behavior detected in terms of microstructures by electrical properties. After calcinated at 700°C for 2h, the samples were processed like pellets under isostatically compaction at 300 MPa, and sintered at 1200°C, 1250°C, 1300°C 1350°C, by 3h. Characterizations were made by x-ray diffraction, scanning electron microscopy with field emission gun and impedance spectroscopy, this last one, as the key tool from this work. The results, in general, showed good densification parameters, which are dependent of x(Er3+) and sintering temperature as well. Furthermore, impedance spectroscopy via equivalents circuits, in terms of the series layer model, revealed the appearance of three microregions, which are stated to be in well agreement with the Core-Shell microstructural model. Considering the relation between the resistive response of each microregion, i.e., the nuclei, the intermediary shells and the grain boundaries, it was possible to establish a path to the relation between PTCR effect with the varistor one under the structural, microstructural and electrical peculiarities from the Ba(1-x)ErxTiO3 electroceramic system, in comparison with the pure polycrystalline BaTiO3 behavior.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Os materiais ferroelétricos têm sido utilizados em muitas áreas da tecnologia e da ciência, pois possuem um grande número de aplicações, como: sensores; transdutores; capacitores; dispositivos ópticos; dentre outras. A busca por novos materiais cerâmicos ferroelétricos tem sido grande. Um dos materiais cerâmicos ferroelétricos mais estudados é o titanato de bário (BT). São vários os métodos de produção e caracterização do titanato de bário. Neste trabalho, pós cerâmicos de titanato de bário foram obtidos por reação do estado sólido a partir de misturas reacionais calcinadas em diferentes temperaturas entre 400C e 900C. Foram três as misturas reacionais: não dopadas; dopadas com 1%; e dopadas com 5% de dióxido de cério (CeO2). A identificação da formação do BT, nos pós cerâmicos produzidos, foi feita a partir de três técnicas de caracterização: difração de raios X (DRX); espectroscopia fotoacústica (PAS); e técnicas de análise térmica. Com a técnica DRX, difratogramas mostraram que a plena formação do titanato de bário ocorreu a partir da temperatura de calcinação de 700C. Para a amostra não dopada com cério e calcinada a 800C, houve deslocamento de todos os picos de difração. Nas amostras dopadas com dióxido de cério houve deslocamento de todos os picos de difração, em relação as amostras não dopadas. Observou-se também que nas amostras dopadas com 5% de CeO2, e calcinadas a 700C e 800C, resíduos de dióxido de cério foram observados nos difratogramas. Com a técnica PAS, espectros de absorção foram obtidos. Foi possível observar uma grande diferença de absorção da amostra calcinada a 600 e 630C, indicando a formação do titanato de bário a partir da temperatura de 630&#61616;C, nas amostras sem a dopagem dióxido de cério. Houve um alargamento nas bandas de absorção a partir da temperatura de 600C, quando o dióxido de cério entrou na matriz. Foi também possível determinar as energias de band-gap das amostras utilizando o método de Tauc. Com as técnicas de análise térmica, em especial através da técnica termogravimétrica (TG/DTG), foi comprovado que até 400C não havia formação de titanato de bário. Visto que nesta temperatura de calcinação houve a maior perda de massa durante a rampa de aquecimento. O início da formação do titanato de bário foi observado a partir da temperatura de calcinação de 500C, assim como nas técnicas DRX e PAS. Portanto, com os resultados apresentados, foi demonstrada a identificação da formação do titanato de bário nas misturas reacionais calcinadas, com auxílio das potencialidades das três técnicas utilizadas. / Ferroelectric materials have been used in many areas of technology and science, because they have a large number of applications, such as sensors; transducers; capacitors; optical devices; among others. The search for new ferroelectric ceramics has been great. One of the most studied ferroelectric ceramic material is barium titanate (BT). There are several methods for production and characterization of barium titanate. In this work, ceramic powders of barium titanate were obtained by solid state reaction from reaction mixtures calcined at different temperatures between 400C and 900C. Three reaction mixtures were used: undoped; doped with 1%; and 5% doped with cerium dioxide (CeO2). The identification of the formation of BT, for the ceramic powders produced, was taken from three characterization techniques: X-ray diffraction (XRD); photoacoustic spectroscopy (PAS); and thermal analysis techniques. With the technique XRD diffraction patterns showed that complete formation of the barium titanate occurred after the calcination temperature of 700C. For the sample not doped with cerium and calcined at 800C, there was displacement of all diffraction peaks. In samples doped with cerium dioxide was no displacement of all diffraction peaks, comparing to undoped samples. It was also observed that the samples doped with 5% CeO2 and calcined at 700C and 800C, cerium dioxide residues were observed in the diffraction pattern. The absorption spectra were obtained with the technique PAS. It was possible to observe a large difference in absorption spectra in the samples calcined at 600C and 630C, indicating the formation of barium titanate at temperature of 630C in the samples without doping of cerium dioxide. There was an enlargement in the absorption band above temperature of 600C when the cerium dioxide was introduced into the matrix. It was also possible to determine the band-gap energy of the samples using the method of TAUC. With thermal analysis techniques, in particular by thermogravimetric technique (TG/DTG), has been proven that up to 400C there was no formation of barium titanate. Once, in this calcination temperature there was the largest mass loss during the heating ramp. The onset of formation of barium titanate was observed from the calcination temperature of 500C, as it has been found by the XRD and PAS techniques. Therefore, with the results presented, the identification of the formation of barium titanate calcined in reaction mixtures with the aid of the potentialities of the three techniques was demonstrated.