B-O Bond Character and Microwave Dielectric Properties of (l-x)CaTiO_3-xCa(Zn_(1/3)Nb_(2/3)O)_3 Perovskite Ceramics

摘要

The relationship between the character of the B-site cation-oxygen bond and the microwave dielectric properties in perovskites dielectric materials was studied in this paper. The atomic net charge of CaTiC>3 (CT) and Ca(Zn_(1/3)Nb_(2/3O_3 (CZN) was calculated respectively. The calculating result implies that the covalency of B-0 bonds in CZN is stronger than that in CT. This predicted that the dielectric constant and loss of the ceramics will decrease after CZN incorporated in CT. To confirme the prediction, (1-x)CT-jcCZN microwave dielectric ceramics were prepared by solid state reaction method with ZnNb_2O_6 as precursor. The structure analysis in terms of tolerance factor gives an identical result as calculation. The microwave dielectric properties, such as dielectric constants, δx/values and τ∫-were studied as a function of composition. With x increasing from 0.2 to 0.8, the dielectric constant linearly decreases from 109 to 49.37, the Q×f value increases from 8,340 to 13,200 GHz, and τ∫ decreases from 321 to -18 ppm/°C. The properties trends are consistent with the previous calculation results, and confirm the relationship between the character of B-0 bond and dielectric properties.