Influence of calcination temperature on characteristics properties of Bi1/2(Na0.8K0.2)1/2TiO3 prepared by sol-gel method

Abstract

This study demonstrated a synthesis of high-crystallinity Bi_1/2(Na_0.8K_0.2)_1/2TiO₃ (BNKT) powders using a sol-gel method through optimizing calcination conditions. Thermogravimetric analysis was utilized to monitor the decomposition and phase evolution of BNKT powders in the calcination temperature (T_cal) range of 600–800 °C. The BNKT powder with a single perovskite crystal phase was obtained by calcining xerogel for 1 h at T_cal = 800 °C. This result was also confirmed by X-ray diffraction and Raman scattering analyses and further explained through the main chemical reaction equations given at each calcination stage of the sol-gel process. In addition, the modification of associated physical properties (microstructure, magnetic, and optical properties) in BNKT powders was also investigated following the structural phase evolution induced by the calcination condition. Furthermore, a single-phase BNKT powder at T_cal = 800 °C was optimal for fabricating bulk ceramics. By sintering the pellets of an optimized powder at 1100 °C for 2 h, the obtained BNKT bulk ceramics showed a dense microstructure with an average grain size of about 1.75 μm. Interestingly, the BNKT bulk ceramics exhibited a high dielectric constant (ε_r) of 2193.4 with a dielectric loss tangent (tanδ) of 0.334 at 1 kHz, room temperature (RT). These findings indicate that optimizing the calcination temperature during the sol–gel process leads to fundamental improvements in the dielectric behavior of bulk BNKT ceramics, providing a promising basis for future studies aimed at enhancing their performance in potential dielectric capacitor applications.

Graphical abstract