Microwave Dielectric Properties and Thermally Stimulated Depolarization Currents of MgF ₂ ‐Doped Diopside Ceramics

Abstract

A new low‐fired dielectric material derived from CaMg 0.9 Zn 0.1 Si 2 O 6 (CMZS) ceramics with high quality factor was synthesized by solid‐state reaction method. The effects of MgF 2 addition on the sinterability, phase composition, crystal defects, and microwave dielectric properties of CMZS were investigated. MgF 2 was proved not only to lower the sintering temperature to ~1000°C but also to remarkably modify the microwave dielectric properties of CMZS. In addition to the main diopside phase, forsterite was identified as the secondary phase in all MgF 2 ‐doped samples. Dielectric temperature spectra showed that MgF 2 induced significant dielectric relaxations associated with oxygen vacancy defects to CMZS. Thermally stimulated depolarization current was, therefore, considered to obtain the defects associated with extrinsic microwave dielectric loss mechanisms. Compared with undoped CMZS, although the concentration of oxygen vacancies showed a notable increase in the 5 wt% MgF 2 ‐doped CMZS, the Q × f values were still improved. Here, with proper MgF 2 ‐doping, it demonstrated that the microwave dielectric loss was basically influenced by phase composition. The excellent characteristics of ε r = 7.78, Q × f = 151 800 GHz, and τ f = −26.40 ppm/°C were achieved from the 5 wt% MgF 2 ‐doped specimens sintered at 1000°C.