Synthesis of Sr0.5Ba0.5Nb2O6 by Coprecipitation Method?Dielectric and Microstructural Characteristics

Strontium barium niobate (Sr0.5Ba0.5Nb2O6) was synthesised by coprecipitation. Aqueous solutions of strontium and barium nitrates and niobium oxalate were added to excess ammonia solution with stirring. The precipitate was calcined at various temperatures. Powder calcined at 1150 C was single phase and 100-250 nm in size. The grain size of sintered compacts increased from 2.5 to 5 micron as the sintering temperature increased from 1250 to 1350 C, and a sintered density of 93% of theoretical was achieved. Grain growth was less than that observed in other synthesis methods, and no abnormal grain growth was observed. This eliminated microcracking problems. A shift in dielectric maxima was observed with frequency when determining the dielectric constant as a function of temperature, showing the relaxor nature of the product. The room temperature dielectric constant was > 2300, whilst the Curie temperature at 1 kHz was in the range 47-60 C, dependent upon sintering conditions. Hysteresis loops were determined at various temperatures. The maximum saturation polarisation of unpoled samples was 2.3 microC/cm2 for samples sintered at 1350 C. The enhanced dielectric and ferroelectric properties were attributed to the enhanced homogeneity provided by the coprecipitation synthesis procedure. 20 refs.