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

This study optimizes the temperature coefficient of resonant frequency (τ f ) in CuMoO 4 ceramics from −36 to −8.82 ppm/°C through W 6+ B-site substitution. XRD analysis confirms the single-phase structure of CuMo 1- x W x O 4 ceramics, while Rietveld refinements reveal an expansion in lattice parameters. W 6+ substitution slightly reduces the relative permittivity (ε r ) due to the changes in sintering density and ion polarizability. Moreover, the internal effects of W 6+ 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- x W x O 4 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.