Vários compostos de fórmula AMO3 (A = Sr, Ca, Ba; M = Ru, Ti, Hf), com estrutura de perovskita foram sintetizados. Realizou-se uma análise estrutural dos compostos, usando difração de raios X, de fonte convencional e síncrotron, e difração de nêutrons em material policristalino. Para esta análise usaram-se dois dos programas mais reconhecidos internacionalmente para o método de Rietveld: DBWS e GSAS. Todas as estruturas analisadas foram classificadas segundo o sistema de inclinação dos octaedros de Glazer e representadas graficamente com o programa Atoms. A estrutura do SrHfO3 foi determinada por difração de nêutrons e raios X em material policristalino. Foi estudada a dependência da estrutura desses compostos com a temperatura e, com a composição, no caso das soluções sólidas SrTi1-xRuxO3 (O≤ x≤1). Duas transições estruturais de fase com a temperatura foram encontradas nos compostos SrRuO3 e SrHfO3. Nas soluções sólidas SrTi1-xRuO3 foi estudada a correlação da estrutura com as propriedades elétricas e com a estrutura eletrônica / Several compounds whose general formula was AMO3 (A = Sr, Ca, Ba; M = Ru, Ti, Hf) and which present the perovskite structure were synthesized. A structural analysis of the compounds by conventional and synchrotron X ray and neutron powder diffraction was performed. For this study was used the internationally accepted software for Rietveld analysis DBWS and GSAS. A11 of the structures analyzed were classified according to the octahedral tilt classification system of Glazer and represented with the program Atoms. The structure of SrHfO3 was determined by neutron and X ray powder diffraction. The dependence of the structure of severa1 compounds with temperature was studied. Two different structural phase transitions were found in the compounds SrRuO3 and SrHfO3. In the case of the solid solutions SrTi1-xRuxO3 (O≤ x ≤1) the dependence of the structure with the composition and the correlation with electric properties and the electronic structure was studied

Vários compostos de fórmula AMO3 (A = Sr, Ca, Ba; M = Ru, Ti, Hf), com estrutura de perovskita foram sintetizados. Realizou-se uma análise estrutural dos compostos, usando difração de raios X, de fonte convencional e síncrotron, e difração de nêutrons em material policristalino. Para esta análise usaram-se dois dos programas mais reconhecidos internacionalmente para o método de Rietveld: DBWS e GSAS. Todas as estruturas analisadas foram classificadas segundo o sistema de inclinação dos octaedros de Glazer e representadas graficamente com o programa Atoms. A estrutura do SrHfO3 foi determinada por difração de nêutrons e raios X em material policristalino. Foi estudada a dependência da estrutura desses compostos com a temperatura e, com a composição, no caso das soluções sólidas SrTi1-xRuxO3 (O≤ x≤1). Duas transições estruturais de fase com a temperatura foram encontradas nos compostos SrRuO3 e SrHfO3. Nas soluções sólidas SrTi1-xRuO3 foi estudada a correlação da estrutura com as propriedades elétricas e com a estrutura eletrônica / Several compounds whose general formula was AMO3 (A = Sr, Ca, Ba; M = Ru, Ti, Hf) and which present the perovskite structure were synthesized. A structural analysis of the compounds by conventional and synchrotron X ray and neutron powder diffraction was performed. For this study was used the internationally accepted software for Rietveld analysis DBWS and GSAS. A11 of the structures analyzed were classified according to the octahedral tilt classification system of Glazer and represented with the program Atoms. The structure of SrHfO3 was determined by neutron and X ray powder diffraction. The dependence of the structure of severa1 compounds with temperature was studied. Two different structural phase transitions were found in the compounds SrRuO3 and SrHfO3. In the case of the solid solutions SrTi1-xRuxO3 (O≤ x ≤1) the dependence of the structure with the composition and the correlation with electric properties and the electronic structure was studied

This thesis deals with the investigations on the atomic composition, chemical surface states and microstructural features of barium titanate and other electronic ceramics namely barium polytitantes, calcium manganites and magnesium calcium titanate by surface analytical techniques. After presenting a brief introduction on the ceramic materials studied in terms of their crystal structures, electrical properties, nonstoichiometry and interfacial characteristics, the thesis describes the synthesis of the ceramics and the methodology of the different surface analytical techniques utilized such as backscattering spectrometry (BS), an ion beam analysis (IBA) technique, X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS). The XPS investigations on the chemical surface states of polycrystalline barium titanate having well-defined electrical characteristics reveal the prevalence of Ba in two distinct chemical environments : the one corresponding to the lower binding energy is related to the dielectric while the other having higher binding energy is correlated to semiconducting properties of the ceramics. Processes such as abrasion or polishing make the surfaces more reactive and susceptible to atmospheric contamination. Sputter cleaning causes surface modification leading to changes in the Ba (3d) and Ti (2p) spectra. Studies on the surface atomic composition by BS and microstructural features of doped barium titanate ceramics reveal their interfacial characteristics in terms segregation of dopants or metal ion constituents. Surfaces of these ceramics exhibit cationic as well as anionic nonstoichiometry depending on the processing steps involved. Ceramics synthesized by oxalate precursor route are Ti-rich while those prepared by gel-to-crystallite method are Ba-rich. These are correlated to the chemical processes and background impurities which in turn control the microstructures. Barium titanate substitued with > 1 at. % Mn are deficient in oxygen and exist as the hexagonal polymorph. Acceptors segregate at the grain boundaries accompanied by the enrichment of Ti leading to PTCR or GBLC characteristics. The oxygen nonstoichiometry prevailing in the surface regions of differently processed calcium manganites is investigated by way of depth profile measurements involving 16O(a,a) 16O resonant scattering. These studies reveal extensive compositional heterogeneity across the surface layers particularly in the manganite specimens annealed in lower po2 leading to the stabilization of brownmillerite phase. Two of the microwave dielectric ceramics namely dibarium nona-titanate and barium tetra-titanate with suitable variations in Ba:Ti ratios have been synthesized by the carbonate-gel precipitation. The corresponding dense ceramics have high permittivity (~ 52) and low temperature coefficient of permittivity (TCK ~ 5 ppm /0C). Extensive miscibility between the ilmenite-type MgTiO3 and perovskite-type CaTiO3 over a wide compositional range is brought about by the simultaneous equivalent substitution of Al3+ + La3+. The resulting (Mg1-(x+y)CaxLay)(Ti1-yAly)O3 ceramics exhibit improved microwave dielectric properties by way of high permittivity, low TCK and high quality factor. The microarea elemental distribution and chemical surface state studies reveal the complexity in the Mg/Ca distribution and its correlation with the solid state miscibility as well as dielectric properties. The discontinuous changes in the local site symmetry of the cationic substituents in these ceramics have been investigated by the photoluminescence spectra using Pr3+ as the emission probe.

The submitted thesis describes characteristics and use of ferroelectric materials which find their utilization in electrotechnical and electronics industry. The thesis is mainly aimed at their behaviour in the electrical field at various intensity. The method using an osciloscope is selected for measuring. For the main measuring in part of this thesis was produced experimental wafer with five samples which were subsequently mesuared. The VEE PRO program was used for creating of collecting datas for histeresis loop and it’s functionality was checked on wafer with five examples in measuring. During this measuring was also measured electric tension dependence of components of complex permittivity.