Effect of MnCO3 on Eliminating Al2TiO5 Phase and Dielectric Properties of 0.90Al2O3–0.10TiO2 Composite Ceramics

The 0.90Al2O3–0.10TiO2 ceramics have been prepared by the conventional solid-state method. MnCO3 was added into the ceramic system for the purpose of eliminating Al2TiO5 and improving the microwave dielectric performance. For the samples of MnCO3 addition, once the sintering temperature was over 1200°C, the Al2TiO5 phase was suppressed without annealing treatment. In combination with scanning electron microscope (SEM) micrographs, the optimized sintering temperature for the ceramics system was 1250°C. The grain size increased with the increasing of MnCO3 addition, accompanied with the abnormal grain growth. Moreover, the energy dispersive spectrometer (EDS) data illustrate that the Mn element exists at the grain boundary. The compact uniform microstructure and excellent microwave dielectric performance were obtained in the samples of 0.90Al2O3–0.10TiO2 with 0.3 mol.% MnCO3 sintered at 1250°C for 4 h: εr = 12.6, Q × f = 125500 GHz, τf = −1.4 ppm/°C.