Synthesis of Sr(0.5)Ba(0.5)Nb(2)0O(6) by coprecipitation method-dielectric and microstructural characteristics

Abstract

Sr0.5Ba0.5Nb2O6 (SBN50) has been synthesized by coprecipitation method using Sr(NO3)(2), Ba(NO3)(2) and Nb-oxalate as precursors and ammonium hydroxide as precipitant. Calcination at 1150degreesC resulted in pure SBN50 phase (XRD) and nano powder with size varying between 100-250 nm (TEM). The average grain size (SEM) in the sintered pellets ranged from 2.5 to 5 mum as the sintering temperature varied from 1250 to 1350degreesC. The maximum sintered density was observed to be 93% of rho(th). The plot of dielectric constant vs. temperature clearly showed a shift of dielectric maxima (epsilon(max)) with frequency, indicating the relaxor nature of SBN50. The room temperature dielectric constant (epsilon(RT) > 2300) observed for all these samples is higher compared to the earlier reported values (epsilon(RT) similar to 1500). The T-c (for 1 KHz) varied from 47-60degreesC depending on the sintering conditions. The hystersis loops were recorded at various temperatures. The maximum saturation polarization for the unpoled pellets was found to be 2.3 muC/cm(2) when sintered at 1350degreesC. The improvement in dielectric and ferroelectric behavior is attributed to the enhanced homogeneity attained by the coprecipitation synthesis route used in the present study. Correlations between microstructure (sintering conditions) and dielectric behavior is explored.