Microwave dielectric characteristics of (Bi1−xSmx)NbO4 ceramics

The effect of sintering temperature on the microwave characteristics of (Bi1−xSmx)NbO4 ceramics was investigated. As the sintering temperature increased from 940 to 1060 °C, the amount of the α-form of (Bi1−xSmx)NbO4 first increased, reached a saturation value, and then decreased. The high temperature form of the (Bi1−xSmx)NbO4 (β-form, triclinic) started to appear at 960 °C for x=0.1, and then its amount increased with the increase of the sintering temperature. The dielectric constant (εr) did not apparently change with the increase of Sm content and saturated at 41.5–42.5. The quality factor (Q×f) reached a maximum value in samples sintered at 1000–1020 °C and then rapidly decreased with the increase of the sintering temperature for x⩾0.1. In samples sintered at >1000 °C, the negative temperature coefficient of the resonant frequency (τf) critically increased with the increase of sintering temperature for all compositions. (Bi1−xSmx)NbO4 ceramics sintered at 960 °C and x=0.1 had a minimum τf value of 1.5 ppm/ °C.