BaTiO3 thick films obtained by tape casting from powders prepared by the oxalate route

BaTiO 3 powders were prepared by co-precipitation via oxalate route. The size, morphology and particle size distribution of the oxalate powders have been optimized by the control of different synthesis parameters during the precipitation reaction (nature of salts, concentration of different solutions, aging time). The single phase BaTiO 3 oxide particles were obtained after a thermal decomposition of the as-synthesized powders at 850°C for 4 hours under air atmosphere. Oxide powders with a suitable specifi c surface area were selected in order to obtain thick fi lms by the tape casting technique. The microstructure and dielectric properties of the thick fi lms varied obviously depending on the deposition-calcination-sintering cycle used. A double deposition- calcination cycle followed by sintering, as well as a two step deposition-calcination-sintering procedure was used in order to improve the compactness and therefore, the dielectric behaviour. A higher dielectric constant value (~ 750) and lower dielectric losses (~ 2 %) were achieved at room temperature and at 1 kHz frequency for the dense, double-deposited fi lm obtained after two deposition-calcination-sintering cycles. For this fi lm, a superior value of the dielectric constant (~ 1100), almost frequency independent in the frequency range of 100 Hz - 10 kHz was gained also at the ferroelectric-paraelectric phase transition temperature of 130°C.