High‐Q Microwave Dielectric Materials Based on the Spinel Mg 2 TiO 4

Composite ceramics based on the spinel Mg 2 TiO 4 were prepared by a conventional mixed‐oxide route. To achieve the temperature stabilization of the dielectric constant, each of the composites was added with 7 mol% CaTiO 3 . The effect of the substitution of isovalent Co for Mg on the microstructure and the microwave dielectric properties of the composite ceramics was also investigated. A maximum Q × f value of around 150–160 THz was obtained for the undoped Mg 2 TiO 4 , whereas a reduced Q × f value was observed for an increase in the Co concentration in the system (1− x )Mg 2 TiO 4 − x Co 2 TiO 4 . Upon doping with 7 mol% CaTiO 3 , the Q × f value passed through a maximum with increasing Co concentration. Adding ZnO–B 2 O 3 to the composite system based on Co‐doped Mg 2 TiO 4 resulted in a reduction of the sintering temperature by 150°–200°C without any significant degradation in the Q × f value.