Phase transition mechanism and long‐term stability of LiF‐assisted sintered Li₂Mg_xZrO_3+x microwave dielectric ceramics

Abstract

Herein, Li2MgxZrO3+x (x = 0–1) +2 wt.% LiF ceramics with a rock salt structure were prepared by the solid‐state reaction method. The phase transition mechanism was systematically investigated by X‐ray diffraction, and first‐principles calculations. With a gradual increase in MgO content, the samples underwent a monoclinic‐Li2ZrO3 to tetragonal‐Li2ZrO3 to tetragonal‐Li2MgZrO4 to cubic‐phase transition. The variations of the microwave dielectric properties due to the phase transition were systematically analyzed by the multi‐phase mixtures law. In addition, CO2 adsorption of the samples was quantitatively analyzed by X‐ray photoelectron spectroscopy, and the long‐term stability of the Q × f of the samples was investigated. The optimal microwave dielectric properties were obtained in Li2Mg0.2ZrO3.2 ceramic at 950°C: εr = 19.5, Q × f = 44 500 GHz, and τf = 2.6 ppm/°C. In addition, the ceramic samples were compatible with Ag, which indicates that Li2MgxZrO3+x (x = 0−1) +2 wt.% LiF is a promising material for low‐temperature co‐fired ceramics.