Effects of MgO and Mg(OH)2 on phase formation and properties of strontium-doped MgTiO3 microwave dielectric ceramics

The effects of MgO and Mg(OH)2 on the phase formation and properties of 0.97MgTiO3-0.03SrTiO3 ceramics were investigated. MgTi2O5 formed in pellets added with MgO (MST) and disappeared in pellets added with Mg(OH)2 (MHST). Abnormal grain growth was observed in MHST due to different reactions during the heating process. Values of εr = 20−22.1, Q × f = 16,500−23,000 GHz and τf = −5.2 to 4.1 ppm/°C and of εr = 17.3−17.7, Q × f = 31,300−48,600 GHz and τf = −9.1 to 0.9 ppm/°C were measured for MST and MHST, respectively. Lower εr for MHST was caused by a lower density. Q × f increased and τf shifted to more negative values when Mg(OH)2 was used instead of MgO.