Structure, microwave dielectric properties, and infrared reflectivity spectrum of W6+ substituted Ce2Zr3(MoO4)9 ceramics

Abstract

A series of trigonal system Ce2Zr3(Mo1-xWxO4)9 (CZM1-xWx) (0.02 ≤ x ≤ 0.10) ceramics with space group R-3c were fabricated by solid-state synthesis method. The impacts of substituting W6+ for Mo6+ on the apparent morphology, structural parameters, microwave dielectric performances, and crystalline phase composition were comprehensively discussed in the CZM1-xWx solid solutions. The X-ray diffraction and classical Rietveld refinement were performed to analysis the crystalline structure, which identified that all the as-synthesized CZM1-xWx ceramic samples only contained a single phase without additional impurities. SEM photographs revealed that clear grain boundaries and well-densified microstructure could be acquired at the optimal temperature of 875 °C for the CZM1-xWx ceramics. Combined with the extrinsic and intrinsic factors, the reduction of εr was associated with porosity, ionic polarizability of primitive unit cell and average bond ionicity. The change in Q·f values could be explained by packing fraction and lattice energy of Mo-site. The variation in τf values were governed by bond valence, bond energy and thermal expansion coefficient of Mo/W–O bond. Besides, the relationship between IR spectra and intrinsic dielectric properties were investigated. In total, the considerable and comprehensive microwave dielectric properties with εr = 10.27, Q·f = 65,553 GHz (at 9.86 GHz), and τf = −10.13 ppm/°C were realized at the low temperature of 875 °C for the CZM1-xWx ceramics with x = 0.04.