Ceramic Materials. Preparation and Dielectric Properties of Ba(Zn1/3Ta2/3)O3-Ba(Zn1/3Nb2/3)O3 Ceramics Modified with Certain Additives.

Abstract

In order to improve sinterability and dielectric properties of Ba(Zn1/3Ta2/3)O3-Ba(Zn1/3Nb2/3)O3 ceramics, the effects of additives on the sintered density and dielectric properties of the (1-x)Ba(Zn1/3Ta2/3)O3-xBa(Zn1/3Nb2/3)O3 ceramics modified with MnO2 and SiO2 additives were investigated. Solid solution ceramics of the system (1-x)Ba(Zn1/3Ta2/3)O3-xBa(Zn1/3Nb2/3)O3+wwt% additive were prepared by the solid state reaction of powder materials, where x=0-1 mole fraction and w=0-0.9 weight%. Ceramic and dielectric properties at low frequency (1MHz) and at microwave frequency (10-13GHz) of the system were studied. The sintered density and dielectric properties of the base composition were improved markedly through the selection of additives in proper amounts. The addition of relatively large amounts (0.7wt%) of MnO2 yielded high density (99% theoretical density) and high relative dielectric constant (42) for the base composition of x=1. High density (99% theoretical density) and high relative dielectric constant (28.9 at 1MHz) were obtained by addition of a small amount (0.1wt%) of SiO2 to the base composition of x=0. This ceramics also showed superior dielectric properties at microwave frequency (the relative dielectric constant of 26.2 and Q of 7500 at 12.948GHz) and very low temperature coefficient of resonant frequency (τf) of -3.3ppm/°C from -40 to 80°C. The microstructure indicated that the ceramics modified with a small amount (0.1-0.2wt%) of SiO2 had a fine, uniform grain structure.