The effect of Mg:Ti ratio on the phase composition and microwave dielectric properties of MgTiO3 ceramics prepared by one synthetic process

In this paper, MgO-CaO-TiO2 based ceramics was prepared by solid-state reaction technique and the effect of Mg:Ti ratio (0.873-1.057) on the phase, microstructure and microwave dielectric properties were investigated. Only two phases MgTiO3 and CaTiO3 appeared in the sample with Mg:Ti = 0.955, and MgTi2O5 and Mg2TiO4 appeared in the sample with Mg:Ti ratio lower and higher than 0.955 respectively. The microstructure showed the dark MgTiO3 grains and the bright grains with three elements Mg, Ca and Ti in the triangle grain boundary. As increasing the ratio of Mg:Ti, the dielectric constant (epsilon(r)) displayed down trend from 21.2 to 20.6, and the Q x f value first increased from 76,300 to 80,000 GHz, thereafter, it declined to 75,000 GHz. Meanwhile, the temperature coefficient of resonant frequency (tau(f)) value first varied from -3.8 to 1.2 ppm/A degrees C and then maintained unchanged. At last, our MgO-CaO-TiO2 based ceramics with Mg:Ti = 0.955 sintered at 1,310 A degrees C for 4 h showed good microwave dielectric properties: epsilon(r) = 21.1, Q x f = 79,915 GHz and tau(f) = 1.2 ppm/A degrees C.