Effects of (Cr1/2Nb1/2)4+-substitution on the chemical bond characteristics, and microwave dielectric properties of cerium zirconium molybdate ceramics

Abstract

A series of Ce2[Zr1−x(Cr1/2Nb1/2)x]3(MoO4)9 (x = 0.02–0.10) ceramics as microwave dielectrics were synthesized and investigated in terms of sintering behaviors, phase compositions, and microwave dielectric properties. The X-ray diffraction data confirmed that the pure phase ceramics were synthesized at 825 °C and all the samples belong to trigonal structure with the R-3c space group. Rietveld refinement was used to achieve the crystal structure parameters by adopting a FULPROF software. The results identified the shrinkage and distortion of [ZrO6] octahedron caused by (Cr1/2Nb1/2)4+ substituted Zr4+. The chemical bond theory was utilized to analyze the relation between chemical bond feature and microwave dielectric properties for understanding the inherent mechanism of the dielectric response. The infrared spectra analysis identified that the spectroscopically determined microwave dielectric loss is consistent with the directly measured, and the inherent loss is mainly derived from the scattering of lattice vibration phonons. Ce2[Zr0.94(Cr1/2Nb1/2)0.06]3(MoO4)9 ceramic obtained at 825 °C for 6 h exhibits considerable properties: relative permittivity (εr) = 10.56, quality factor (Q × f) = 73,224 GHz, and temperature coefficient of resonant frequency (τf) = −7.96 ppm/°C. It indicates that the substitution of (Cr1/2Nb1/2)4+ is an effective way to optimize microwave dielectric materials.