To modify the near-zero temperature coefficient of resonant frequency ( τ f ) of CaWO 4 -based materials and explore their structure–property relationships, Ca 1− x Nd x W 1− x Nb x O 4 (CWNN x ) ceramics were prepared. Phase evolution occurred in the system from tetragonal-scheelite to monoclinic-fergusonite at x =0.7. Relative permittivity ( ε r ) increased from 11.28 to 16.84, influenced by the polarizability per unit molar volume ( α / V m ), whereas the negative deviations between ε r,corr and ε r,C−M (Δ ε r ≈ −3.39% to −12.50%) resulted from the compression effect of Ca 2+ and Nd 3+ coupled with Nb 5+ at the B site. The quality factor ( Q ) rose by 52%, attributed to the decreased Raman full width at half-maximum and increased lattice energy ( U ). The τ f values changed from −27.6×10 −6 to 72.1×10 −6 °C −1 , governed by the increased temperature coefficient of ionic polarizability ( τ αm ), decreased coefficient of thermal expansion ( α L ), and weakened A-site compression. CWNN0.3 ceramic demonstrated superior properties ( ε r =13.00, Q × f =60170 GHz, and τ f =−1.9×10 −6 °C −1 ), suggesting potential applications in sub-6 GHz antennas.
XIANG et al. (Wed,) studied this question.