Effects of (Mg1/3Nb2/3) substitution on the structure and microwave dielectric properties of Sr2TiO4 ceramics

Abstract Sr 2 Ti 1- x (Mg 1/3 Nb 2/3 ) x O 4 (0 ≤ x ≤ 0.4) solid solutions were synthesized by standard solid-state reaction method for the first time, and their microwave dielectric properties were systematically investigated together with the microstructure. X-ray diffraction patterns revealed the formation of solid solutions in the whole composition range, while two kinds of secondary phases started to appear when x = 0.4. With increasing x , the dielectric constant ( e r ) was tuned from 42 to 26.3 and the temperature coefficient of resonant frequency ( τ f ) could be successfully modified from 130ppm/ o C to 46.3ppm/ o C. Excellent combination of microwave dielectric properties with e r = 28.5, Qf = 83,300GHz, and τ f = 53ppm/ o C were obtained for the x = 0.3 composition after sintering at 1500°C for 3h.