Optimization of microstructure and dielectric properties of BCTZ-based ceramics using two-step sintering method

In this study, the (Ba, Ca)(Ti, Zr)O3-based dielectric ceramics were prepared by the two-step sintering method. The effects of the first step sintering temperature (T1) on microscopic morphology and dielectric properties were investigated in detail. The two-step sintering method could effectively reduce the grain size and form a uniformly distributed microstructure. As a result, the temperature coefficient of capacitance (TCC) and the breakdown strength (BDS) were improved obviously, compared with the traditional one-step sintering. The finite element simulation of ceramics obtained by COMSOL was used further to reveal the functions of the different sintering conditions. When the optimum T1 was chosen, the average grain size decreased to 0.53 mu m, with a simulated breakdown time of 0.78 s, the TCC was - 45.8% to 1.8% during the temperature range of - 30 to 85 degrees C and the BDS reached 165 +/- 0.5 kV/cm, accompanied by a high dielectric constant (epsilon r) of 6841 +/- 103 and a low dielectric loss (tan delta) (0.51% +/- 0.03%).