A‐ and B Site Cosubstituted Ba6−3xSm8+2xTi18O54Microwave Dielectric Ceramics

Abstract

Tin (Sn) substitution into the B‐site and Nd/Sn cosubstitution into the A‐ and B‐sites were investigated in a Ba 6−3xSm8+2xTi18O54solid solution (x= 2/3). A small amount of tin substitution for titanium improved the temperature coefficient of resonant frequency (τf) but led to a decrease of the relative dielectric constant (ɛ) and the quality factor (Qf). The Ba6−3xSm8+2x(Ti1−zSnz)18O54‐based tungsten‐bronze phase became unstable for compositions with a tin content of ≥10 mol%, where BaSm2O4and Sm2(Sn,Ti)2O7appeared, and finally, these phases became the major phases. On the other hand, Nd/Sn cosubstitution led to a good combination of high ɛ, high Qf, and near‐zero τf. Excellent microwave dielectric properties were achieved in Ba6−3x(Sm1−yNdy)8+2x(Ti1−zSnz)18O54ceramics with y= 0.8 and z= 0.05 sintered at 1360°C for 3 h: ɛ= 82, Qf= 10 000 GHz, and calculated τf=+17 ppm/°C. The tolerance factor and electronegativity difference exhibited important effects on the microwave dielectric properties, especially the Qf value. A large tolerance factor and high electronegativity difference generally led to a higher Qf value.