Defect structure of BaTiO3-based ceramics

E. BRZOZOWSKI; W. SALGUEIRO; A. SOMOZA; M.S. CASTRO

Foz do Iguazú

Congreso; 11th International Meeting on Ferroelectricity; 2005

A study of the defect structure of BaTiO3-based ceramics is presented. Samples were prepared from commercial BaTiO3 powders with the addition of 0.05, 0.15, 0.30, and 0.60 mol% of Nb2O5, Sb2O3 or La2O3. Starting powders were mixed by stirring in alcoholic medium with a high-speed turbine at 6000 rpm for 5 min. After drying, mixtures were crushed into powders and sieved through a 100 µm mesh screen. Finally, isostatically pressed cylinders (200 MPa) were sintered at 1350°C for 2 h. X-ray diffraction studies of the BaTiO3 samples were carried out on sintered samples. From the (002) and (200) diffraction profiles, a semi quantitative study of the cell distortion was performed. EPR spectroscopy was used to characterise the paramagnetic species in the crushed samples. Information regarding bulk and vacancy-like defects in the specimens studied was also obtained using positron annihilation lifetime spectroscopy. It was found that concentration and type of additive influence the BaTiO3 defect profile. The presence of titanium vacancies was detected in samples with high additive content instead barium vacancies were detected in samples with a low additive content. Furthermore, oxygen vacancies were recorded in samples with antimony addition. A relationship among the doping level, defect structure and cell distortion is proposed.