Effect of Process Parameter Optimization in Reducing Sintering Temperature in the Synthesis and Characterization of Ba(Zn1/3Nb2/3)O3

Controlling the cooling rate during calcination and sintering, phase pure perovskite Ba(Zn1/3Nb2/3)O3 has been prepared by simple solid state reaction route with density >93% at relatively low sintering of 1175°C making it compatible for microwave dielectric applications. The samples are characterized by X-ray diffraction analysis and scanning electron microscopy. The X-ray diffraction shows pure perovskite phase with cubic structure. The lattice constants were obtained a = 4.1032？？. Detailed studies of ε′ and ε′′ show that the compound exhibits dielectric anomaly at 430°C. Material shows distributed relaxation at higher temperature. Impedance analysis revealed that the impedance is mainly due to the grains. AC conduction activation energies are estimated from Arrhenius plots, and conduction mechanism is discussed. 1. Introduction Ba(Zn1/3Nb2/3)O3 (BZN) is a very promising lead free perovskite material for electroceramics applications owing to its interesting dielectric properties. It can be used for various applications such as to the dielectric resonators [1–3]. ？Much research on BZN ceramics has been targeted to find alternate for the Ta-based complex perovskite ceramics such as Ba(Zn1/3Ta2/3)O3 and Ba(Mg1/3Ta2/3)O3 because of the expensive Ta2O5. One major problem in using BZN lies in the fact that it needs a high sintering temperature to reach a satisfactory final density 1350°C [4, 5]. Chemical processes such as sol-gel and precipitation method were also used to reduce the sintering temperature of the ceramics [6–8]. Sintering temperature of BZN ceramic can also be reduced by the use of additives such as B2O3 and CuO. However, BaB4O7 and BaB2O4 secondary phases were observed in the B2O3 added BZN [9]. ？？Although the microwave dielectric properties of the BZN ceramic are very promising, the sinterability remains an issue. In this work, we attempted the optimization of process parameters in simple solid state reaction route. We successfully prepared Ba(Zn1/3Nb2/3)O3 in pure perovskite phase with high density (>93%) at relatively low sintering temperature without using additives. This has been achieved by simply controlling the rate of cooling and heating during calcination and sintering. Structural, dielectric, and electrical impedance analyses of prepared BZN ceramics are investigated and compared with those reported earlier. 2. Experimental Procedure Ba(Zn1/3Nb2/3)O3 was prepared by two-step solid state reaction route or columbite method. First, columbite structure was formed by prereacting Nb2O5 (99.9% Loba Chemie Pvt. Ltd., India) with ZnO