Effects of MgO and Mg(OH)₂ on Phase Formation and Properties of MgTiO₃ Microwave Dielectric Ceramics

Abstract

This study investigates the effects of MgO and Mg(OH)₂ on the phase formation and properties of MgTiO₃ ceramics prepared via a reaction-sintering process. A mixture of raw materials was sintered into MgTiO₃ ceramics by bypassing calcination and subsequent pulverization stages. The second phase MgTi₂O₅ forms in pellets with added MgO (MT) and disappears in pellets with added Mg(OH)₂ (MHT). Abnormal grain growth is observed in MHT due to different reactions during the heating process. Microwave dielectric properties ε _r = 18.5–19.2, Q × f = 53,300–76,300 GHz and τ _f = −58.7 to −53.2 ppm/°C are measured for MT. ε _r = 15.3–15.9, Q × f = 118,800–144,400 GHz and τ _f = −52.8 to −49.8 ppm/°C are measured for MHT. The lower ε _r for MHT is caused by a lower density. Q × f increases and τ _f shifts to less negative values when Mg(OH)₂ is used instead of MgO. The reaction-sintering process is then a simple and effective method to produce MgTiO₃ ceramics for applications in microwave dielectric resonators.