Studies of dielectric characteristics of BaBi_2Nb_2O_9 ferroelectrics prepared by chemical precursor decomposition method

摘要

BaBiNb_2O_9 (BBN) powders in the nanometer range were prepared by chemical precursor decomposition method (CPD). TG-DTA showed that precursor sample got freed from organic contaminants at 575 deg C. XRD showed that a single phase with the layered perovskite structure of BBN was formed after calcining at 600 deg C. No intermediate phase was found during heat treatment at and above 600 deg C. The crystallite size (D) and the effective strain (eta) were found to be 26 nm and 0.000867, respectively, while the particle size obtained from TEM was 28 +- 2 nm. SEM revealed that the average grain size after sintering at 900 deg C for 4 h was approx 1.67 mu m. A relative density of approx 93 percent was obtained using a two-step sintering process at moderate pressure. Dielectric and ferroelectric properties were investigated in the temperature range 50-500 deg C and frequencies from 1 kHz to 5 MHz. Strong dispersion of the complex relative dielectric constant was observed including typical relaxor features such as shift of permittivity maximum with frequency and broadening of the peak maximum. The high dielectric constant of 545 measured at 100 kHz and other properties of BBN ceramics were compared to that of BBN prepared by other conventional methods and found to be superior.