Effect of Sn4+ substitution on the dielectric properties of Bi2O3–ZnO–Nb2O5 pyrochlores

Abstract

As a promising candidate for thermostable LTCC material with NP0 characteristic, (Bi1.8Zn0.2)(Zn0.5Nb1.5−xSnx)O7.15−x/2 (x=0.0, 0.05, 0.1, 0.2) dielectric ceramics with improved dielectric properties were prepared by conventional mixed oxide route. The effects of Sn4+ ion substitution on the dielectric properties based on structural characteristics in this system were investigated systematically. Rietveld refinement was used to analyse the structure change of the sintered samples. Microscopic analysis showed that all of the samples maintained the (Bi1.5Zn0.5)(Zn0.5Nb1.5)O7 phase. The dielectric constant εr was related to relative density. The B-site cations bond valence of (Bi1.8Zn0.2)(Zn0.5Nb1.5−xSnx)O7.15−x/2 ceramics was calculated to evaluate the relationship between the temperature coefficient of the dielectric constant τε and the structural characteristics of the B site cations in a new way. And the loss tangent tanδ was mainly affected by the grain size and grain boundaries in this system. The (Bi1.8Zn0.2)(Zn0.5Nb1.5−xSnx)O7.15−x/2 (x=0.1) ceramics with high dielectric constant of εr=170 and near-zero temperature coefficient of τε=0.3747ppm/°C were obtained at a low sintering temperature of 1000°C, which can be a promising candidate for low temperature co-fired ceramics (LTCC) and multilayer components applications in high frequency and microwave range.