Sol-gel synthesis of nano-scaled BaTiO3, BaZrO3 and BaTi0.5Zr0.5O3 oxides via single-source alkoxide precursors and semi-alkoxide routes

Sol-gel synthesis of nano-sized BaTiO3, BaZrO3 and BaTi0.5Zr0.5O3 ceramics using alkoxide and semi-alkoxide routes has been investigated and the pervo skites obtained have been compared with respect to crystallisation temperat ure, crystallite size and compositional purity. Heterometal alkoxides conta ining two (for BaTiO3 and BaZrO3) and three (for BaTi0.5Zr0.5O3) different metals were used as single-source precursors in the alkoxide route while se mi-alkoxide synthesis was performed by reacting barium hydroxide or acetate with Ti and/or Zr alkoxides. Semi-alkoxide synthesis also produces stoichi ometric and phase-pure oxides, however, at temperatures higher than 1000 de grees C. At temperatures below 1000 degrees C, BaCO3 and small amounts of o ther undesired phases (e.g., BaTi2O4) were present in the oxides derived fr om semi-alkoxide synthesis. Thermal behaviour, studied by TGA/DTA measureme nts, shows that thermal decomposition occurs in three major steps and depen ds on the educt composition and the synthesis route. Among alkoxide derived powders, crystalline BaTi0.5Zr0.5O3 phase is formed at 400 degrees C while complete crystallisation of BaMO3 ceramics occurs around 600 degrees C. Th e cubic to tetragonal phase transition for BaTiO3 is clearly observed at re latively low-temperature of 800 degrees C. The stoichiometry and phase homo geneity of the obtained powders were demonstrated by energy dispersive X-ra y analysis and powder diffractometry. The averaged crystallite size of the obtained nano-ceramics was evaluated using the FormFit programme. SEM and T EM observations revealed a high microstructural uniformity.