Phase transition mechanism and long‐term stability of LiF‐assisted sintered Li₂MgxZrO₃₊x microwave dielectric ceramics

Herein, Li 2 Mg x ZrO 3+ 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‐Li 2 ZrO 3 to tetragonal‐Li 2 ZrO 3 to tetragonal‐Li 2 MgZrO 4 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, CO 2 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 Li 2 Mg 0.2 ZrO 3.2 ceramic at 950°C: ε r = 19.5, Q × f = 44 500 GHz, and τ f = 2.6 ppm/°C. In addition, the ceramic samples were compatible with Ag, which indicates that Li 2 Mg x ZrO 3+ x ( x = 0−1) +2 wt.% LiF is a promising material for low‐temperature co‐fired ceramics.