SYNTHESIS OF LEAD FREE SODIUM BISMUTH TITANATE (NBT) CERAMIC BY CONVENTIONAL AND MICROWAVE SINTERING METHODS

Abstract

Dielectric studies were carried out on a lead free Sodium Bismuth Titanate, NBT, ( Na _0.5 Bi _0.5 TiO ₃) composition. The material was synthesized by conventional ceramic method (CS) and microwave sintering (MS). The presence of single phase has been confirmed by X-ray diffraction and scanning electron microscopy of NBT ceramic. The later technique (MS) resulted in material with high density, dielectric properties and improved microstructure. The transition temperature was observed slightly higher for microwave sintered (MS) material. Longitudinal modulus measurements are very sensitive property to identify the phase transitions in ceramics. Longitudinal modulus (L) measurements were also employed on these samples in the frequency 136 kHz and can be studied in the wide temperature range 30°C to 400°C. The elastic behavior (L) showed a break at two temperatures (~200°C and 350°C) in both the conventional and microwave sintered ceramics. In NBT ceramics, permittivity anomalies are connected to modulus anomalies. The results are correlated with the dielectric measurements. This behavior explained in the light of structural phase transitions in the ferroelectric ceramics.