Crystal structure and enhanced microwave dielectric properties of the Ce₂[Zr_1-x(Al_1/2Ta_1/2)_x]₃(MoO₄)₉ ceramics at microwave frequency

Dense microwave dielectric ceramics of Ce₂[Zr_1-x(Al_1/2Ta_1/2)_x]₃(MoO₄)₉ (CZMAT) (x = 0.02-0.10) were prepared by the conventional solid-state route. The effects of (Al_1/2Ta_1/2)⁴⁺ on their microstructures, sintering behaviors, and microwave dielectric properties were systematically investigated. On the basis of the X-ray diffraction (XRD) results, all the samples were matched well with Pr₂Zr₃(MoO₄)₉ structures, which belonged to the space group $R\overline{3}c.$ The lattice parameters were obtained using the Rietveld refinement method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips-Van Vechten-Levine (P-V-L) theory. Excellent dielectric properties of Ce₂[Zr_0.94(Al_1/2Ta_1/2)_0.06]₃(MoO₄)₉ with a relative permittivity (ɛ_r) of 10.46, quality factor (Q × f ) of 83,796 GHz, and temperature coefficient of resonant frequency (τ_f) of -11.50 ppm/℃ were achieved at 850 ℃.