W6+ doped CuMoO4 ceramics with low dielectric permittivity and near-zero temperature coefficient of resonant frequency for ULTCC application

Abstract

This study optimizes the temperature coefficient of resonant frequency (τ_f) in CuMoO₄ ceramics from −36 to −8.82 ppm/°C through W⁶⁺ B-site substitution. XRD analysis confirms the single-phase structure of CuMo_1-xW_xO₄ ceramics, while Rietveld refinements reveal an expansion in lattice parameters. W⁶⁺ substitution slightly reduces the relative permittivity (ε_r) due to the changes in sintering density and ion polarizability. Moreover, the internal effects of W⁶⁺ substitution on the Q×f value are systematically investigated by analyzing the Raman peak's full width at half maximum (FWHM) and conducting packing fraction calculations. Additionally, lattice distortion and bond valence analyses elucidate the intrinsic mechanism behind τ_f improvement. Consequently, when x = 0.08, CuMo_1-xW_xO₄ sintered at 625°C exhibits superior overall performance: ε_r = 5.13, Q×f = 65,506 GHz, τ_f = −8.82 ppm/°C. Furthermore, it demonstrates good chemical compatibility with Al electrodes making the material more suitable for ULTCC practical applications.