A‐ and B Site Cosubstituted Ba 6−3 x Sm 8+2 x Ti 18 O 54 Microwave Dielectric Ceramics

Tin (Sn) substitution into the B‐site and Nd/Sn cosubstitution into the A‐ and B‐sites were investigated in a Ba 6−3 x Sm 8+2 x Ti 18 O 54 solid solution ( x = 2/3). A small amount of tin substitution for titanium improved the temperature coefficient of resonant frequency (τ f ) but led to a decrease of the relative dielectric constant (ɛ) and the quality factor ( Qf ). The Ba 6−3 x Sm 8+2 x (Ti 1− z Sn z ) 18 O 54 ‐based tungsten‐bronze phase became unstable for compositions with a tin content of ≥10 mol%, where BaSm 2 O 4 and Sm 2 (Sn,Ti) 2 O 7 appeared, 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 τ f . Excellent microwave dielectric properties were achieved in Ba 6−3 x (Sm 1− y Nd y ) 8+2 x (Ti 1− z Sn z ) 18 O 54 ceramics with y = 0.8 and z = 0.05 sintered at 1360°C for 3 h: ɛ= 82, Qf = 10 000 GHz, and calculated τ f =+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.