Microwave dielectric ceramics (MWDCs) with low dielectric constant and low dielectric loss are desired in contemporary society, where the communication frequency is developing to high frequency (sub-6G). Herein, Nd₂(Zr_1−xTi_x)₃(MoO₄)₉ (NZ_1−xT_xM, x = 0.02–0.10) ceramics were prepared through a solid-phase process. According to X-ray diffraction (XRD) patterns, the ceramics could form a pure crystal structure with the R $\overline{3}$c (167) space group. The internal parameters affecting the properties of the ceramics were calculated and analyzed by employing Clausius–Mossotti relationship, Shannon’s rule, and Phillips–van Vechten–Levine (P–V–L) theory. Furthermore, theoretical dielectric loss of the ceramics was measured and analyzed by a Fourier transform infrared (IR) radiation spectrometer. Notably, when x = 0.08 and sintered at 700 ℃, optimal microwave dielectric properties of the ceramics were obtained, including a dielectric constant (ε_r) = 10.94, Q·f = 82,525 GHz (at 9.62 GHz), and near-zero resonant frequency temperature coefficient (τ_f) = −12.99 ppm/℃. This study not only obtained an MWDC with excellent properties but also deeply analyzed the effects of Ti⁴⁺ on the microwave dielectric properties and chemical bond characteristics of Nd₂Zr₃(MoO₄)₉ (NZM), which laid a solid foundation for the development of rare-earth molybdate MWDC system.

In this study, a sequence of Ce₂[Zr_1-x(Co_1/2W_1/2)_x]₃(MoO₄)₉ (CZ_1-x(CW)_xM) (x = 0.02–0.10) ceramics with excellent microwave dielectric properties were obtained by the traditional solid-phase method. The crystal structure, dielectric properties, and chemical bond characters of the ceramics were characterized and analyzed. X-ray diffraction and Rietveld refinement analysis show that CZ_1-x(CW)_xM could form a single-phase of the triangular crystal system in the entire doping range. The microstructure of the ceramic samples was obtained by scanning electron microscopy. The sintering temperature was reduced and the gain of the sample was refined as the increase of doping ion content. Furthermore, the intrinsic factors affecting the properties of CZ_1-x(CW)_xM were analyzed by employing P-V-L theory and through in-depth infrared analysis. When x was 0.04 and the sintering temperature was 750 ℃, the best dielectric properties of the samples were achieved, including ε_r = 9.95, Q·f = 80, 803 GHz (at 9.99 GHz), and τ_f = − 9.10 ppm/℃.