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

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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 1150°C 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 μm as the sintering temperature varied from 1250 to 1350°C. The maximum sintered density was observed to be 93% of ρth. The plot of dielectric constant vs. temperature clearly showed a shift of dielectric maxima (εmax) with frequency, indicating the relaxor nature of SBN50. The room temperature dielectric constant (εRT > 2300) observed for all these samples is higher compared to the earlier reported values (εRT ∼ 1500). The Tc (for 1 KHz) varied from 47–60°C 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 μC/cm2 when sintered at 1350°C. 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.

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