The preparation of lead-free bismuth sodium titanate ceramics via the solid state combustion technique

ABSTRACT

Low calcined temperature, high density and good dielectric properties of BNT ceramics successfully prepared by the solid state combustion technique and glycine was used as fuel to reduce the reaction temperature. The effects of calcination temperature (500–900°C) and sintering temperature (1100–1150°C) on phase formation, microstructure and dielectric properties of (Bi_0.5Na_0.5)TiO₃ (BNT) ceramics were investigated. The phase purity, crystal structure and microstructure of the samples were tested using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that the pure rhombohedral perovskite structure of BNT powders were observed from the sample calcined at 650°C, which is lower than the solid state reaction technique by ∼200°C. The purity phase was detected in all ceramic samples. The microstructure of the BNT powders exhibited an almost-spherical morphology and a highly agglomerated form. The average grain size of the ceramics was increased with increase sintering temperature. The T_F-R and T_m were slightly increased with the increase of sintering temperature. The highest density and the best dielectric properties was obtained by sample sintered at temperature of 1120°C. The solid state combustion technique is a new alternative for reduction of calcined temperature, improvement of densification and modify of dielectric properties to prepared BNT ceramics.

KEYWORDS:

• Bismuth sodium titanate
• phase formation
• microstructure
• dielectric properties
• combustion technique

5. Acknowledgments

This work was supported by the Higher Education Research Promotion and National Research University project of Thailand, Office of the Higher Education Commission. The authors wish to thank the Department of Physics, Faculty of Science, Naresuan University for their supporting facilities. Thanks are also given to Dr. Kyle V. Lopin for his help in editing the manuscript.