Currently available solid lubricants only perform well under a limited range of environmental conditions. Unlike them, oxides are thermodynamically stable and relatively inert over a broad range of temperatures and environments. However, conventional oxides are brittle at normal temperatures; exhibiting significant plasticity only at high temperatures (>0.5Tmelting). This prevents oxides' use in tribological applications at low temperatures. If oxides can be made lubricious at low temperatures, they would be excellent solid lubricants for a wide range of conditions. Atomic layer deposition (ALD) is a growth technique capable of depositing highly uniform and conformal films in challenging applications that have buried surfaces and high-aspect-ratio features such as microelectromechanical (MEMS) devices where the need for robust solid lubricants is sometimes necessary. This dissertation investigates the surface and subsurface characteristics of ALD-grown ZnO/Al2O3 nanolaminates and ZrO2 monofilms before and after sliding at room temperature. Significant enhancement in friction and wear performance was observed for some films. HRSEM/FIB, HRTEM and ancillary techniques (i.e. SAED, EELS) were used to determine the mechanisms responsible for this enhancement. Contributory characteristics and energy dissipation modes were identified that promote low-temperature lubricity in both material systems.

Master’s thesis are concerned with the cutting ceramic materials and its ef-fective usage. The first part of the thesis is focused on the general properties of the cutting ceramics, its history, development, production and description of the various types. This part includes as well a description of the mechanic-physical properties and the potential of the usage for machining. The second part of the work solves the general evaluation of the cutting power. The main issue in the next part is the identification of cutting ceramics range and the selection accor-ding to main world producers. The fourth part deals with the assessments and the comparison of the working conditions for different types of the machined ma-terials. The technical economic assessment shows the potentials in the total pro-duction costs reduction.

Thesis dealing with cutting ceramics and its efficient use. Introduction describes the general characteristics of the cutting of ceramics, its history and development and production of various kinds. This section describes the mechanical and physical properties with potential application in machining. The se-cond part is an overview of cutting-frame in the range of selected world leaders. Ano-ther section focuses on general assessment of the power of cutting tools and other ma-terials comparison. The fourth part, is comparing the working conditions of producers and tools intended for cutting.

High dielectric constant materials are of technological importance as they lead to the miniaturization of the electronic devices. For instance, in the case of memory devices based on capacitive components, such as static and dynamic random access memories, the dielectric constant will ultimately decide the level of miniaturization. In this context, the observation of anomalously high dielectric constant (>10) in the double perovskite Sr2SbMnO6 (SSM) over wide frequency (100 Hz1 MHz) and (190373 K) temperature range has attracted a great deal of attention. However, unfortunately their dielectric losses were also high which limit their use for possible capacitor and related applications. The dielectric loss however was known to decrease with decreasing crystallite size in electroceramics. Therefore, the present work has been focused on the synthesis of nanocrystalline SSM powders by moltensalt route. The characterization of the ceramics fabricated from these powders for their microstructural and dielectric properties. A cubic phase of SSM powder was obtained by calcining the as synthesized powders at 900°C/10h by using sulphate flux. The crystallite size was ~ 60 nm. The activation energy associated with the particle growth was found to be 95 ± 5 kJmol-1 . The ceramic sintered at 1075°C/16h exhibited high dielectric constant (>10at 1 kHz) with low loss (0.72 at 1 kHz) at room temperature. The results are interpreted in terms of a twolayer model with conducting grains partitioned from each other by poorly conducting grain boundaries. Using this model, we attributed the two electrical responses in impedance and modulus formalisms to the grain and grain boundary effects, respectively, while the detected Debyelike relaxation and large dielectric constant were explained in terms of MaxwellWagner relaxation.

Relaxor ferroelectrics have been a subject of intense research owing to their interesting physical properties such as high dielectric constant and giant electro-striction. Unlike the conventional lead based relaxors, the relaxors belonging to Aurivillius family of oxides have received much less attention because of the poor understanding of the origin of the relaxor behavior and high processing temperatures involved. In the present investigations, an attempt has been made to understand the origin of relaxor behavior of the materials belonging to Aurivillius family of oxides. The structure and relaxor behavior of BaBi2Nb2O9 (BBN) has been established via the XRD, electron diffraction and dielectric spectroscopy. The results are compared with that of a normal ferroelectric like SrBi2Nb2O9 belonging to the same family as well with that of a conventional relaxor like PMN. The results indicate that the dielectric behavior of BBN is significantly different from that of the conventional relaxors like BBN with very slow broadening of relaxation times and was attributed to the absence of significant polar ordering. To substantiate the existing understanding, studies have been carried out by adopting different strategies such as B-site and A-site cationic substitutions and texturing of the ceramics. Vanadium doping on B-site was found to decrease the sintering temperatures significantly. Aliovalent La3+ doping was found to affect the dielectric behavior strongly with substantial decrease of the freezing temperature and dielectric constants which shows that the relaxor behavior of BBN is highly sensitive to A-site order-disorder. The (00l) textured ceramic of pure and vanadium doped BBN was fabricated via a simple melt-quenching technique and was found to exhibit a significant dielectric and pyroelectric anisotropy. A new class of relaxor compositions (K0.5La0.5Bi2Nb2O9 & K0.5La0.5Bi2Ta2O9) have been synthesized and characterized. These new compounds exhibited interesting physical properties which are akin to that of the conventional lead based relaxors. The presence of superlattice reflections in the electron diffractin patterns recorded on these compounds establish the presence of polar nano regions of significant size. These relaxor crystallites at nano/micro level embedded in a glass matrix have been found to be very promising from their physical properties view point.

Rare-earth ions co-doped lanthanum fluoride (LaF3) nanoparticles (NPs) were synthesized and the effect of different annealing temperatures investigated. We have also investigated the thermo-optical properties of Tm3+ and Eu3+ doped Y2O3 transparent ceramics. The LaF3:Yb3+/Ho3+ and LaF3:Yb3+/Tm3+ NPs were treated thermally by 3 hs at 300, 500, 700, and 900 °C and then characterized with respect to crystalline structures, sizes, shapes, presence of other crystalline phases and luminescent properties. From the experimental results, optimization of optical and structural properties were obtained for the thermal treatment at 500 °C while maintaining the LaF3 crystalline phase. However, it was observed the formation of lanthanum oxifluoride (LaOF) under thermal annealing at 900 °C, with higher luminescence in the near infrared, which makes this host to deserve further study. It was also synthesized LaF3 NPs varying the Tm3+ and Ho3+ ions concentrations with fixed Yb3+ one and these samples were thermally treated at 500 and 900 °C by 3 hs. The 1.2, 1.47, 1.8, and 2 μm emissions behaviors of Tm3+ and Ho3+ ions were investigated, in order to obtain the best concentrations for these emissions in these two hosts: LaF3 and LaOF. We also synthesized Yb3+/Tm3+ and Yb3+/Ho3+ co-doped LaF3 using nitrate and chloride precursors and these samples were annealed at 500 and 900° C to observe what occurs in the structural, morphological, and optical properties of the LaF3 and LaOF. As a result, no significant difference was observed in their structural and optical properties, thus facilitating the use of nitrate and chloride precursors for further researches using these hosts. Another very interesting and promising material is the yttrium oxide (Y2O3) transparent ceramics. In this case, we investigated using the thermal lens technique, conventional spectroscopy of luminescence and temporal dynamic, the thermal and optical properties of Y2O3:Tm3+ and Y2O3:Eu3+. The thermal properties obtained were: thermal diffusivity =26.06x10-3cm2/s, thermal conductivity =5.8 W/m.K, and the temperature coefficient of the optical path length change ⁄=2.978x10-6K-1. Small values for D and k were obtained in comparison to those of the literature, and this was attributed to the grain size of the investigated ceramics. The luminescence decays along with the thermal lens spectroscopy results were complementary to a complete characterization of the Y2O3:Tm3+ ceramics, enabling obtaining the fluorescence quantum efficiency of the Tm3+ 3F4 level emitting at 1.8 μm, which was estimated at η1=0.84. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nanopartículas (NPs) de fluoreto de lantânio (LaF3) codopadas com íons terras-rara foram sintetizadas e avaliado o efeito de tratamento térmico em diferentes temperaturas. Também investigamos as propriedades termo-ópticas de cerâmicas transparentes de Y2O3 dopadas com os íons Tm3+ e Eu3+. As NPs de LaF3:Yb3+/Ho3+ e LaF3:Yb3+/Tm3+ foram tratadas termicamente por 3 horas nas temperaturas de 300, 500, 700 e 900 °C para então caracterizá-las com relação as suas estruturas cristalinas, tamanhos, formas, presença de outras fases cristalinas e propriedades luminescentes. A partir de resultados experimentais, verificou-se a otimização das propriedades estrutural e óptica no tratamento térmico de 500 °C, mantendo a fase cristalina de LaF3. No entanto, foi observada à formação de óxifluoreto de lantânio (LaOF) no tratamento térmico a 900 °C, resultando em maior luminescência no infravermelho próximo, o que faz essa matriz merecer um estudo mais aprofundado. Também, foram sintetizadas NPs de LaF3, mudando a concentração dos dopantes Tm3+ e Ho3+, mantendo fixa a de Yb3+, e essas amostras foram tratadas termicamente a 500 e 900 °C por 3 horas. Foram investigados os comportamentos das emissões em 1,2; 1,47; 1,8 e 2 μm dos íons Tm3+ e Ho3+, com intuito de se obter as melhores concentrações para essas emissões nessas duas matrizes: LaF3 e LaOF. Sintetizamos também LaF3 codopadas com Yb3+/Tm3+ e Yb3+/Ho3+, usando precursores nitratos e cloretos e as tratamos termicamente a 500 e 900 °C para se observar o que ocorre nas propriedades estruturais, morfológicas e ópticas nas matrizes LaF3 e LaOF. Como resultado, não foram observadas diferenças significativas em suas propriedades estruturais e ópticas, facilitando assim o uso de precursores nitratos e cloretos para futuras pesquisas usando essas matrizes. Outra matriz promissora é a cerâmica transparente de óxido de ítrio (Y2O3). Neste caso, investigamos usando a técnica de lente térmica e espectroscopia convencional de luminescência e dinâmica temporal, as propriedades térmicas e ópticas de Y2O3:Tm3+ e Y2O3:Eu3+. As propriedades termo-ópticas obtidas foram: difusividade térmica =26,06×10-3 cm2/s, condutividade térmica =5,8 W/m.K e o coeficiente de variação do caminho óptico com a temperatura ⁄=2,978×10-6 K-1. Valores pequenos para D e foram obtidos, quando comparados com os da literatura. Tais valores foram atribuídos ao tamanho dos grãos das nossas cerâmicas. Os decaimentos das luminescências, juntamente com os resultados da espectroscopia de lente térmica, foram complementares para uma caracterização completa da cerâmica de Y2O3:Tm3+, possibilitando a obtenção da eficiência quântica de fluorescência do nível 34 do íon Tm3+ emitindo em 1,8 μm, a qual foi estimada em 1=0,84.

Povrchy inorganických materiálov, zvlášť kovov alebo kovových oxidov, ktoré sú často charakteristické vysokou povrchovou energiou, sú zvyčajne kontaminované adsorbovanými organickými molekulami. Tieto molekuly majú na povrchy zväčša nepriaznivý vplyv, do značnej miery napríklad ovplyvňujú funkcionalitu a výkonnosť polovodičov a znemožňujú, prípadne sťažujú prevedenie povrchových úprav na povrchoch kovov aj keramík. Taktiež majú nepriaznivý vplyv na priľnavosť. Adsorbované častice spôsobujú znižovanie hydrofilicity povrchu. Hydrofilicita, adhezivita a zmáčavosť povrchu sa veľmi dobre posudzujú prostredníctvom merania kontaktného uhlu. V tejto práci je značná pozornosť venovaná práve meraniu statického kontaktného uhlu. [10] Samotné meranie kontaktného uhlu je možné vykonať rôznymi spôsobmi, v tejto práci bol však použitý najvhodnejší prístup, a to metódou „sessile-drop“, teda pokladanej alebo depozitovanej kvapky na meraný povrch. K meraniu bol využitý klasický „sessile-drop goniometer“, teda aparatúra, ktorá pozostávala z nastaviteľného stojanu na vzorky, nad ktorým bol umiestnený zdroj svetla, a objektívu fotoaparátu, ktorý bol prepojený s kamerou zabudovaného smartfónu. Meranie prebiehalo tak, že kvapka s objemom 3L destilovanej superčistej vody bola depozitovaná na povrch substrátu pomocou mikroinjekčnej striekačky. Cieľom tejto práce bolo nielen stanoviť kontaktné uhly a porovnať ich hodnoty medzi rôznymi typmi materiálov navzájom a po upravách tepelného a/lebo chemického charakteru. Vyhodnotené údaje zachycovali zmeny, ku ktorým došlo na povrchoch daných keramických materiálov pri adsorpcii organických molekúl. Proces tepelnej úpravy (kalcinácia na teplote 800°C, následne pokles na teplotu 600°C, po celkovú dobu 16 hodín) bol aplikovaný na všetkých typoch vzoriek, kde niektoré sa medzi sebou líšili teplotou slinovania. Ihneď po kalcinácii boli vzorky podrobené meraniu kontaktných uhlov, z ktorého jasne vyplynulo, že hydrofilicita a zmáčavosť povrchu sa zvýšila. Tento jav bol pozorovaný na všetkých vzorkách, a na všetkých vzorkách sa hodnoty kontaktného uhlu líšili veľmi významne od hodnoty, ktorá bola získaná v tzv. primárnom meraní. Všetky detailné hodnoty a vyhodnotené výsledky sú posudzované v časti diskusia. Ďalšou úpravou povrchu, ktorá bola vykonaná na vybraných vzorkách, bolo čistenie povrchu etanolom. Proces bol opäť realizovaný na všetkých vzorkách. Potom, ako boli zrealizované všetky merania na kalcinovaných vzorkách, boli všetky tieto vzorky ponorené do etanolu na približne 2 hodiny. Po vybratí vzoriek a ich osušení na vzduchu boli uskutočnené ďalšie merania kontaktných uhlov. Výsledky priniesli opäť rozdielne hodnoty v porovnaní s predchádzajúcimi meraniami a sú rozvinuté v časti diskusia.

Bismuth layer-structured ferroelectrics have received significant attention recently due to their fairly high TC and good fatigue endurance which make them important candidates for non-volatile ferroelectric random access memories (Fe-RAMs) as well as for the piezoelectric device applications at high temperatures. Structure of these compounds is generally described as the pseudo-perovskite block (An-1BnO3n+1)2- sandwiched between the bismuth oxide layers (Bi2O2)2+ along the c-axis, where n represents the number of corner sharing BO6 octahedra forming the perovskite-like slabs. Only a few compounds belonging to this family show relaxor behavior (frequency dependent diffuse phase transition). Relaxor ferroelectrics are very attractive for a variety of applications, such as capacitors, sensors, actuators, and integrated electromechanical systems. The present work attempts to understand the mechanism of relaxor behavior in Aurivillius oxides as well as to improve the piezoelectric and ferroelectric properties of some of the known phases. Details pertaining to the fabrication and characterization of BaBi4Ti4O15 (n = 4 member of Aurivillius family of oxides) ceramics are presented. X-ray diffraction, Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were employed to probe the structural and microstructural details. The contribution of irreversible domain wall movement to the room temperature dielectric constant and polarization was quantitatively evaluated using the nonlinear dielectric response. Dielectric dispersion and conduction mechanism of these ceramics are also explicated using the complex impedance spectroscopy. The effects of La3+ and Ca2+ doping on the phase transition behavior and other properties of BaBi4Ti4O15 are investigated. La3+ doping for Bi3+ was found to strengthen the relaxor behavior. New compounds such as CaNaBi2Nb3O12, SrNaBi2Nb3O12, Na0.5La0.5Bi4Ti4O12, etc. belonging to the Aurivillius family of oxides have been synthesized and investigations concerning their structural, dielectric and ferroelectric properties are presented. Rietveld refinement of room temperature X-ray powder data suggested that CaNaBi2Nb3O12 and SrNaBi2Nb3O12crystallize in the orthorhombic space group B2cb. SrNaBi2Nb3O12 ceramics exhibited frequency-dependent Tm which follows the Vogel-Fulcher relation implying a relaxor nature. No frequency dependence of Tm was observed for CaNaBi2Nb3O12 ceramics. Polarization - electric field hysteresis loops recorded well above Tm confirmed the coexistence of polar and non-polar domains in SrNaBi2Nb3O12 ceramics. Dielectric anomaly observed around 675 K for CNBN corresponds to the ferroelectric to paraelectric phase transition which is accompanied by the change in crystal structure from orthorhombic to tetragonal. Fe and Nb co-doped Bi4Ti3O12 ceramics were fabricated and characterized for their structural, electrical and magnetic properties.