Novel zinc manganese oxide-based microwave dielectric ceramics for LTCC applications

Abstract Low-temperature co-fired ceramics (LTCCs), with a Zn(Mn1−xTix)3O7 (0≤x≤1.0) composition, were prepared using a conventional solid-state method. A novel ZnMn3O7 ceramic was obtained, with a ZnMn2O4 spinel structure, er of 7.32, Q×f of 13,667 GHz, and τf of −58.33 ppm/°C. The effect of various dopant concentrations on the microstructure and microwave dielectric properties of the material was investigated. Results showed that the increase in dopant concentration changed the phase composition, improved the microwave dielectric properties, and reduced the sintering temperature of the Zn(Mn1−xTix)3O7 by a factor of 250 °C. The dielectric constant of Zn(Mn1−xTix)3O7 varied from 7.32 to 33.08 at x=0.8. However, the maximum value was reduced to 27.67 at x=1.0. Moreover, the value of Q×f increased significantly up to a maximum value of 18,934 GHz, whereas τf changed gradually from −58.33 ppm/°C to +289.25 ppm/°C. In addition, promising LTCC materials with stable temperature characteristics and co-firing compatibility with silver electrodes can be obtained in the nominal Zn(Mn1−xTix)3O7 (x=0.68) ceramics with 5 wt% ZnO–B2O3 glass sintered at 900 °C. This material possesses the following microwave dielectric properties: er of 18.2, Q×f of 12,018 GHz, and τf of −3.98 ppm/°C.