Made available in DSpace on 2014-06-11T19:32:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-26Bitstream added on 2014-06-13T20:42:52Z : No. of bitstreams: 1 aguiar_ec_dr_araiq.pdf: 2825912 bytes, checksum: 6b9c3aa9260f3f9e3707127beafc008a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / No presente trabalho foram preparados pós cerâmicos de Bi4Ti3O12 estequiométrico, com excesso de bismuto e com excesso dopados com nióbio pelo método dos precursores poliméricos. As fases cristalinas foram obtidas por calcinação a 700 °C-4h com 10% excesso Bi nas composições Bi4Ti3-xNbxO12 (x = 0; 0,1; 0,2 e 0,4 mol% Nb). Os pós obtidos foram caracterizados quanto ao tamanho das partículas, difratometria de raios X, espectroscopias Raman, no infravermelho e UV-vis indicando pós nanométricos com fase ortorrômbica predominante, ordenados a curta e longa distância e com alta cristalinidade. As cerâmicas foram compactadas e sinterizadas em forno convencional e microondas a 800 °C, além de caracterizadas por medidas de condutividade elétrica, constante e perda dielétricas, histerese e microscopia eletrônica de varredura. A condutividade elétrica sofreu decréscimo nas cerâmicas dopadas com nióbio, apresentando constante dielétrica de 170 na temperatura ambiente, baixos valores de polarização remanescente e densidade relativa máxima de 93% para cerâmicas sinterizadas em microondas. Cerâmicas funcionais texturizadas foram obtidas empregando-se a técnica de tape casting (colagem de folhas), onde partículas templates do BIT sintetizadas via método dos sais fundidos e com alta orientação na direção do eixo c foram adicionados as barbotinas aquosas do titanato de bismuto. As medidas de caracterização indicaram grau de texturização das cerâmicas de até 80% na direção do eixo c, com aumento da densidade relativa (97%) , da polarização remanescente (3,4 µC/cm2 ) além de menor condutividade elétrica, boa resposta dielétrica e microestrutura com grãos orientados, em comparação às cerâmicas policristalinas / In the present study were prepared stoichiometric Bi4Ti3O12 ceramic powders, with excess bismuth and niobium doped from polymeric precursor method. The crystalline phases were obtained by calcination at 700 °C for 4h with 10% excess Bi in the compositions Bi4Ti3- xNbxO12 (x = 0, 0.1, 0.2 and 0.4 mol% Nb). The powders were characterized for particle size, X-ray diffraction, Raman, IR and UV-vis spectroscopy indicating a predominant nanosized orthorhombic phase ordered at short and long distances, with high crystallinity. The ceramics were compacted and sintered in a conventional and microwave oven at 800 °C, and characterized by measurements of electrical conductivity, dielectric constant and loss, hysteresis, and scanning electron microscopy. The electrical conductivity decreased in the niobium-doped ceramics, with dielectric constant of 170 at room temperature, low remanent polarization and relative density of up to 93% for ceramics sintered in the microwave oven. Functional textured ceramics were obtained using the tape casting methodology where particles of the BIT templates synthesized from the molten salts method presented high orientation in the c-axis direction were added to the aqueous slurry of bismuth titanate. Characterization measures indicated texturing degree of ceramics up to 80% along the c- axis, with increasing in relative density (97%), in the remanent polarization (3.4 µC/cm2) and lower electrical conductivity, good dielectric response and microstructure with grain oriented compared to polycrystalline ceramics

Orientador: José Arana Varela / Banca: Mário Cilense / Banca: Valmor Roberto Mastelaro / Banca: Daniel Zanetti de Flório / Banca: Eliana Navarro dos Santos Muccillo / Resumo: No presente trabalho foram preparados pós cerâmicos de Bi4Ti3O12 estequiométrico, com excesso de bismuto e com excesso dopados com nióbio pelo método dos precursores poliméricos. As fases cristalinas foram obtidas por calcinação a 700 °C-4h com 10% excesso Bi nas composições Bi4Ti3-xNbxO12 (x = 0; 0,1; 0,2 e 0,4 mol% Nb). Os pós obtidos foram caracterizados quanto ao tamanho das partículas, difratometria de raios X, espectroscopias Raman, no infravermelho e UV-vis indicando pós nanométricos com fase ortorrômbica predominante, ordenados a curta e longa distância e com alta cristalinidade. As cerâmicas foram compactadas e sinterizadas em forno convencional e microondas a 800 °C, além de caracterizadas por medidas de condutividade elétrica, constante e perda dielétricas, histerese e microscopia eletrônica de varredura. A condutividade elétrica sofreu decréscimo nas cerâmicas dopadas com nióbio, apresentando constante dielétrica de 170 na temperatura ambiente, baixos valores de polarização remanescente e densidade relativa máxima de 93% para cerâmicas sinterizadas em microondas. Cerâmicas funcionais texturizadas foram obtidas empregando-se a técnica de tape casting (colagem de folhas), onde partículas templates do BIT sintetizadas via método dos sais fundidos e com alta orientação na direção do eixo c foram adicionados as barbotinas aquosas do titanato de bismuto. As medidas de caracterização indicaram grau de texturização das cerâmicas de até 80% na direção do eixo c, com aumento da densidade relativa (97%) , da polarização remanescente (3,4 µC/cm2 ) além de menor condutividade elétrica, boa resposta dielétrica e microestrutura com grãos orientados, em comparação às cerâmicas policristalinas / Abstract: In the present study were prepared stoichiometric Bi4Ti3O12 ceramic powders, with excess bismuth and niobium doped from polymeric precursor method. The crystalline phases were obtained by calcination at 700 °C for 4h with 10% excess Bi in the compositions Bi4Ti3- xNbxO12 (x = 0, 0.1, 0.2 and 0.4 mol% Nb). The powders were characterized for particle size, X-ray diffraction, Raman, IR and UV-vis spectroscopy indicating a predominant nanosized orthorhombic phase ordered at short and long distances, with high crystallinity. The ceramics were compacted and sintered in a conventional and microwave oven at 800 °C, and characterized by measurements of electrical conductivity, dielectric constant and loss, hysteresis, and scanning electron microscopy. The electrical conductivity decreased in the niobium-doped ceramics, with dielectric constant of 170 at room temperature, low remanent polarization and relative density of up to 93% for ceramics sintered in the microwave oven. Functional textured ceramics were obtained using the tape casting methodology where particles of the BIT templates synthesized from the molten salts method presented high orientation in the c-axis direction were added to the aqueous slurry of bismuth titanate. Characterization measures indicated texturing degree of ceramics up to 80% along the c- axis, with increasing in relative density (97%), in the remanent polarization (3.4 µC/cm2) and lower electrical conductivity, good dielectric response and microstructure with grain oriented compared to polycrystalline ceramics / Doutor

Les matériaux piézoélectriques ont été étudiés en détails du fait de la versatilité des applications industrielles possibles (accéléromètres, gyroscopes ou transducteurs). Les bonnes propriétés piézoélectriques (d33=510pC/N) de Pb(Yb½Nb½)O₃-PbTiO₃ (PYN-PT) et sa haute température de Curie (~370°C à la MPB). Cette solution solide entre une double pérovskite (ordonné sur le site B) et le titanate de plomb est remarquable, du fait qu'elle présente tous les ordres polaires à température ambiante: antiferroélectricité, ferroélectricité et des propriétés relaxeurs.Dans le cadre de ce travail de thèse, je présente les résultats obtenus sur des céramiques de PYN-PT de diverses compositions à travers le diagramme de phase. A partir des mesures de diffractions de rayons X et de diffusion neutronique, de spectroscopie diélectrique ainsi que des mesures piézoélectriques et ferroélectriques, un nouveau diagramme de phase sera proposé.Cette étude minutieuse du diagramme de phase a montré que celui-ci est plus compliqué que ce que laissait apparaître la littérature. En particulier, la structure de l'antiferroélectrique PYN est particulière en comparaison des autres pérovskites antiferroélectriques au plomb. En effet, dans PYN, les atomes de plomb sont déplacé suivant la direction du vecteur de modulation et les cations B sont en dehors de leurs positions prototypiques et participe à l'ordre antipolaire observé.De plus, la zone morphotropique (x _0.50) s'étale sur une zone en compositions beaucoup plus grande que ce qui a été observé dans d'autres solutions solides à base de plomb. Dans la zone pauvre en PT de la zone morphtropique, l'absence de phase rhomboédrique (attendue par analogie avec les autres systèmes au plomb) a été démontré.D'autre part, parmi les compositions présentant des propriétés relaxeurs, des différences sont apparues et il est proposé que, dans la solution solide PYN-PT, plusieurs types de relaxeurs existent.Finalement, je propose un modèle expliquant continument le changement d'ordre polaire dans le diagramme de phase. Ce modèle est basée sur la corrélation des déplacements de plomb induite par la nature chimique et l'arrangement cationique du site B. / Piezoelectricity has attracted a considerable amount of work due to the variety of possible applications such as accelerometers, gyroscopes or transducers. Pb(Yb½Nb½)O₃-PbTiO₃ is long known to have large piezoelectric properties (d33=510pC/N) and a relatively high Curie temperature (_370°C at the MPB).This solid solution between a double (B-site ordered) perovskite (Pb2YbNbO6) and lead titanate is remarkable, in the sense that it presents all polar orders. Indeed, depending on the composition, the solid solution can exhibit at room temperature: antiferroelectric, classical ferroelectric or relaxor properties. In this work, I will present results obtained on PYN-PT ceramics of various compositions spanning the phase diagram. From experiments using X-ray diffraction and neutron scattering, dielectric spectroscopy, as well as piezoelectric and ferroelectric measurements as a function of temperature, a new phase diagram is proposed. This thorough study of the phase diagram of PYN-PT has revealed a more complex phase diagram than what was reported in the literature. In particular, the structure of the antiferroelectric PYN is peculiar compared to the other Pb-based antiferroelectric. Indeed, in PYN, the Pb atoms are displaced along the direction of the modulation vector and that the B cations are not in their prototypic positions and take part in the antipolar order observed.Moreover, the morphtropic phase boundary (x _0.50) extends over a larger compositional range than what was observed in other Pb-based solid solution. In the PT-poor side of the morphtropic phase boundary, the absence of the expected rhombohedral phase (by analogy with the other Pb-based solid solutions) was demonstrated. Furthermore, among the compositions presenting relaxor properties, differences have arisen and I suggest that several types of relaxors exist, in the PYN-PT solid solution. Finally, I will propose a model explaining continuously the change of polar order through out the phase diagram. This model is based on the correlation of Pb displacements induced by the chemical nature and the cationic arrangement on the B site.

Esta dissertação descreve os métodos empregados na preparação por solução de filmes de copolímeros P(VDF-TrFE) nas composições molares 60/40, 70/30 e 80/20. Foram utilizadas as técnicas de deposição por centrifugação (spin coating deposition) e de espalhamento por extensor, usando acetona e metil-etil-cetona (MEK) como solventes. Filmes de boa qualidade só foram obtidos quando se acelerou o processo de evaporação do solvente, através da passagem de um fluxo de ar seco na câmara onde os filmes eram produzidos. Medidas de espectroscopia de infra-vermelho confirmaram a ausência de solvente nos filmes, já que observou-se que o pico 1715 cm-1 (carbonilha) característico do MEK não aparece nos resultados com filmes. A caracterização dos filmes fabricados foi feita através de medidas de calorimetria diferencial exploratória de varredura (DSC), difração de raios-X, espectroscopia de infra-vermelho e cromatografia líquida por exclusão de tamanho (GPC). Nos termogramas de DSC puderam ser identificadas as transições de fase ferro-paraelétrica (na temperatura de Curie, Tc) e de fusão. Os valores de Tc e da temperatura de fusão, Tf, encontrados são consistentes com os valores da literatura, com Tc aumentando com o conteúdo de VDF, ao passo que o oposto ocorre com Tf, devido ao fato que o aumento do percentual de TrFE na região cristalina aumenta a estabilidade da fase paraelétrica. Os difratogramas de Raios-X apresentaram, basicamente, um ombro largo correspondente à porção amorfa do filme, e um pico alto e estreito devido a parte cristalina do filme. No ajuste dos difratogramas através de uma função de Lorentz modificada, os resultados para as amostras de 60/40 e 70/30 foram ajustadas com três picos, o que parece indicar que pode haver duas fases cristalinas para estas amostras. Já os resultados para a amostra de 80/20 foram ajustados com apenas dois picos. O tratamento térmico das amostras, a diversas temperaturas, mostrou influenciar fortemente as propriedades dos filmes. Os seus efeitos mais importantes são o aumento da temperatura de Curie e da percentagem de cristalinidade do filme com a temperatura de tratamento / This dissertation describes the experimental methods employed in the fabrication of thin films (up to 40 micra) of the copolymer P(VDF-TrFE) for three different VDF contents, Viz. 60/40, 70/30 and 80/20. The copolymers were dissolved in either acetone or methyl-ethyl-ketone(MEK) and deposited on a solid substrate using spin coating or a sliding-knife. Good quality films could only BR obtained after dry air was flushed into the chamber where the films were fabricated. Infra-red spectrocopy measurements confirmed the abscene of solvent in the samples, as the 1715 cm-1 peak from MEK is not present in the results for the films. The film characterization was carried out using differential scanning calorimetry (DSC), X-ray diffraction, infra-red spectrocopy and gel permeation chromatography (GPC). Phase transitions could be identified in the DSC thermography which can be related to the ferro-paraelectric transition (at the Curie temperature, Tc) and to the melting of the sample. The values for Tc and the melting temperature, Tf), were consistent with those published in the literature, with Tc increasing with the contents of VDF, while the opposite is true for Tf because the increase in the TrFE contents causes the stability of the paraelectric phase to increase. The X-ray diffractograms displayed, basically, one broad halo due to the amorphous part of the film, and a eak due to its crystalline region. The diffractograms were fitted using a modified Lorentz function, where three peaks had to be assumed for the 60/40 and 70/30 samples. This appears to indicate that there may exist two crystalline phases in these samples. The results for 80/20 samples, on the other hand, were fitted with two peaks. The thermal treatment of the samples, under various temperatures, proved to influence strongly the properties of the films. Its main effects are the increase in the Curie temperature and the increase in the degree of crystallinity of the films with increasing temperature of thermal treatment

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Neste trabalho, foram investigadas as propriedades estruturais e dielÃtricas da fase monoclÃnica da cerÃmica ferroelÃtrica Na2Nb4O11 com adiÃÃo de Ãxido de bismuto (Bi2O3) nas proporÃÃes de 2, 5 e 10% em massa. Os pÃs Na2Nb4O11 foram produzidos pelo mÃtodo convencional de reaÃÃo em estado sÃlido. ApÃs a calcinaÃÃo, as amostras foram prensadas na forma de pastilhas cilÃndricas e, em seguida, sinterizadas. O estudo da estrutura e da composiÃÃo das amostras foi feito atravÃs de difraÃÃo de raios-X e Refinamento Rieteveld e um estudo da morfologia foi realizado atravÃs de Microscopia EletrÃnica de Varredura onde visualmente, as amostras lembram as medidas de densidade obtidas atravÃs da picnometria. A caracterizaÃÃo dielÃtrica foi realizada na faixa de radiofrequÃncias e de microondas. Em ambos os casos, foi realizado um estudo das propriedades em relaÃÃo à variaÃÃo da temperatura para possÃvel aplicaÃÃo em dispositivos de RF e MW. Nosso interesse foi obter dielÃtricos cerÃmicos com permissividade dielÃtrica alta, baixas perdas dielÃtricas e estabilidade tÃrmica. Nas medidas realizadas em temperatura ambiente de 25ÂC obtivemos um alto valor da permissividade dielÃtrica (εâr = 250,9) com o NN10Bi (10% de Bi2O3) em 10 kHz e um valor da tangente de perda, relativamente baixo (tanδ = 1,80.10-2) com o NN2Bi (2% de Bi2O3) em 1 MHz. Em temperatura variÃvel e numa frequÃncia fixa de 100 kHz, obtivemos um alto valor da permissividade dielÃtrica com εâr = 440,78 a 440ÂC com o NN2Bi e um valor de perda dielÃtrica em torno de 1,81.10-1 a 280ÂC com o NN10Bi. A medida do coeficiente de temperatura da frequÃncia de ressonÃncia mostrou a possibilidade de atingir a estabilidade tÃrmica = 0 com o aumento do nÃvel de adiÃÃo de Bi2O3. Para o NN00 obtivemos um tauf = -3378,42 ppm/ÂC. Com a adiÃÃo do Bi2O3, este valor vai se aproximando do zero e atinge tauf = -250,04 ppm/ÂC para o NN10Bi. As medidas na faixa de microondas foram obtidas utilizando-se o mÃtodo Hakki-Coleman. Uma simulaÃÃo numÃrica foi realizada com cada amostra verificando-se a reciprocidade com os dados experimentais. Neste estudo obtivemos uma cerÃmica NN10Bi, Ãtil para a aplicaÃÃo em dispositivos de antenas omnidirecionais de baixo ganho, em sistemas de comunicaÃÃes via satÃlite, internet sem fio, radar, forno de microondas, recepÃÃo de rÃdio e em projetos de espaÃonaves. / In this present work, Na2Nb4O11, ferroelectric ceramics have been investigated by their monoclinic phase structural and dielectric properties have been enhanced by the addition of 2, 5 and 10 wt% Bismuth. Na2Nb4O11 powders have been produced by conventional solid-state reaction method. Milling process was carried out by using a high energy planetary mill. The calcined powders were thoroughly weighted and pressed using an axial press to make cylinder pellets for sintering. The single-phase Na2Nb4O11 was determined by X-Ray Diffraction (XRD) technique and Rietveld refinement method, while morphology, crystal structure and phase composition were determined via Scattering Electron Microscopy (SEM) where the samplesâ crystal structure micrographs show nearly the density measures obtained by Pycnometry technique. Dielectric characterization was carried out over a radiofrequency (RF) and microwave (MW) range. Both cases, we have studied the properties related to temperature variation for likely applications to RF and MW devices. We have focused on obtaining dielectric ceramics with high dielectric permittivity, low dielectric loss and near-zero temperature coefficient of resonant frequency. Room temperature measures at 25ÂC have had a high permittivity value = 250.9) for NN10Bi (10% of Bi2O3) at 10 kHz and a dielectric loss, relatively low value 1.80 10-2 for NN2Bi (2% of Bi2O3) at 1MHz. Varying temperature and fixed frequency at 100 kHz, we have obtained a high dielectric permittivity value 440.78 at 440ÂC) for NN2Bi and a dielectric loss about 1,81.10-1 at 280ÂC for NN10Bi. Near-zero temperature coefficient of resonant frequency has shown possibility of reaching thermal stability = 0 as increasing Bi2O3 addition level. For NN00 we have obtained = - 3378.42 ppm/oC. More Bi2O3 addition provides = - 250.04 ppm/oC for NN10Bi. Microwave measures were carried out using Hakki Coleman technique. A numerical simulation was also achieved for each sample for verifying the similarity to experimental data. In this study we have obtained NN10Bi ceramics, applicable for low-gain antenna devices, for satellite communication systems, wireless internet, radar, microwave oven, radio frequency receptor and spacecraft designing.

O objetivo deste trabalho foi implementar um sistema para a determinação do coeficiente piroelétrico em materiais poliméricos. O método consiste em variar a temperatura da amostra de forma senoidal e medir a corrente em função do tempo. Através do sinal da corrente elétrica e da sua diferença de fase com a temperatura, separa-se a corrente elétrica de origem piroelétrica, a partir da qual se determina o coeficiente piroelétrico. Apresenta-se a caracterização do sistema abrangendo aspectos como o intervalo de temperatura das medidas e amplitude e freqüência da oscilação da temperatura. O método foi empregado para realizar medidas exploratórias com o polímero ferroelétrico poli(fluoreto de vinilideno), PVDF, polarizado pela aplicação de uma rampa de tensão, e com o polímero poli(metacrilato de metila), PMMA, com corante polar, polarizado com o triodo de corona. Nas medidas foram variados os parâmetros do processo de polarização elétrica tais como o campo elétrico máximo e a temperatura / An experimental setup to measure the pyroelectric coefficient of polymers was implemented. The method is based on the measurement of the electric current generated by the sample when its temperature was set to oscillate sinusoidally. Using the measured current and its phase difference related with the temperature thepyroelectric current was obtained, from that the pyroelectric coefficient was determined. It is shown the characterization of the experimental system such as the temperature amplitude and frequency interval of operation. The method was applied in exploratory measurements employing the ferroelectric polymer poly(vynilidene fIuoride), PVDF, poled by a ramp voltage, and the poly(methyl metacrylate), PMMA, having a polar dye, poled with the carona triode. Measurements were performed far different poling conditions such as the maximum applied field and temperature

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23502号 / 工博第4914号 / 新制||工||1768(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 平方 寛之, 教授 北條 正樹, 教授 嶋田 隆広, 教授 井上 康博 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19684号 / 工博第4139号 / 新制||工||1639(附属図書館) / 32720 / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 北村 隆行, 教授 立花 明知, 教授 鈴木 基史 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This dissertation is focused on ferromagnetic, multiferroics, and two-dimensional (2D) perovskites, exploring different unique collective magnetic and ferroic characters: (1) ferromagnetic thin film Co/Pd multilayers, (2) BaTiO3-BiFeO3 (BTO-BFO) a magneto-electric materials system, and (3) CuCl4 halide organic-inorganic perovskites. Low-power all-optical memory offers a unique opportunity to achieve ultra-fast magnetic switching in which the switching dynamics are not thermally mediated and occur on the order of the laser pulse. However, it is challenging to achieve a low-power optically excited magnetization precession angle above 90 degrees, which is required for magnetic switching. Co/Pd thin film multilayers were investigated for their potentially large perpendicular magnetic anisotropy (PMA) with three differing regimes of magnetic anisotropy: in-plane, weakly out-of-plane, and out-of-plane. Utilizing the time-resolved magneto-optical Kerr effect (TR-MOKE), we observed clear magnetic precession (on the order of a few GHz) with magnetic precession angle increasing (up to 4.5 degrees) for thinner Co samples which demonstrated stronger PMA. We observed a clear connection between PMA strength and precession amplitude as well as a large efficiency of energy transfer between spin and orbital subsystems for our strongest PMA sample. BTO-BFO is a strong room-temperature multiferroic with enhanced magneto-electric properties compared to BFO. We utilized time-resolved differential reflectivity (TR-DR) and TR-MOKE to observe strong coherent acoustic phonons in thin films as well as nanorods. Our nanorods showed additional modes (a new 20 GHz and 6 GHz mode) not observed in thin films including the fast 33 GHz mode which showed some weak tunability with high magnetic fields (up to 10 T). The observed tunability of these modes in an external magnetic field shows interesting coupling between magnetic moment and phononic modes which may be caused by the breaking of the spin-cycloid at the interface of the nanorods and the surface of the nanorods. We also observed second harmonic generation (SHG) emission which demonstrated a large enhancement in our nanorod structures with further observation of wavelength dependence. Finally, ferromagnetic resonance on our nanorod and thin film BTO-BFO structures indicated very weak Gilbert damping (on the order of 10−3), demonstrating the practicality of our structure for low-spin loss applications. Lastly, this dissertation focuses on a project around CuCl4 and CuCl2Br2 perovskites in which we observed time-dependent SHG. An increase in SHG as a function of infrared laser exposure is shown to coincide with changes in the crystal structure of the Cu perovskite materials. This increase in SHG was shown to last for a few days after hours of laser exposure indicating a slow hysteretic change to the crystal structure of the perovskites. / Doctor of Philosophy / Multifunctionality in materials is important for various applications including future mem- ory devices where ferromagnetism (collective magnetic order), ferroelectricity (collective electric polarization order), and piezoelectricity (collective strain order) can be implemented in a given device. This dissertation centers on three material systems for exploring ferroic orders: Co/Pd thin multilayers, BaTiO3-BiFeO3 (BTO-BFO) films and nano-rod arrays, and Cu halide organic-inorganic perovskite thin films and 2D structures. Co/Pd thin films demonstrate interesting ferromagnetic order with magnetic anisotropy in which the magnetization of the thin film has a preferred direction based on the thickness of the thin film. BTO-BFO demonstrates coupling between ferroelectric and antiferromagnetic order. The magnetic information may be controlled by applying electric fields or strain and Cu halide perovskites demonstrate potentially created ferroelectric order under long-term laser expo- sure with high ferroelectric switching speeds. Dynamics and nonlinear optical responses in these materials systems were explored with Ti:Sapphire pulsed lasers (∼ 100 fs). Our techniques allowed us for a better understanding of fast carrier and spin dynamics after optical excitation. Furthermore, nonlinear optics, in which two or more photons can be used to emit higher energy photons, were employed to explore the ferroelectric properties within these material systems. The results presented in this dissertation provided information on collective orders and fundamental interactions in several less-explored material systems.

Electrical conduction mechanisms in BaTiO₃-based ferroelectric capacitor ceramics with an emphasis on the X7R type were studied. Dominant charge carriers in this material were identified as conduction band electrons below a temperature of 850°C. This was substantiated by the following results: negative Seebeck coefficients, zero galvanic cell voltage, and evidence of space charge-limited currents in MLC capacitors and related ceramic. Effects of chip thickness on the electrical parameters, as well as the I-V characteristics, were studied. Chip electrical parameters such as resistivity, dielectric constant, and activation energy were found to be independent of chip thickness. Effects of ambient were also studied and differences in current-voltage behavior were attributed to surface effects. Complex impedance spectroscopy proved to be a useful technique in separating grain, grain boundary, and contact contributions to the total impedance. Impedance plots for X7R ceramic revealed negligible contact impedance. The most probable electrical transport mechanism in X7R ceramic is small polaron hopping, although the possibility of combining small polaron hopping and grain boundary transmission cannot be excluded. / Ph. D.