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

Keywords: BaTiO3 , Co-precipitation , Tape-casting , Thick lm , Dielectric permittivity

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Abstract:

BaTiO3 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 BaTiO3 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 speci c surface area were selected in order to obtain thick lms by the tape casting technique. The microstructure and dielectric properties of the thick lms varied obviously depending on the deposition-calcination-sintering cycle used. A double depositioncalcination 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 lm obtained after two deposition-calcination-sintering cycles. For this 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.

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