Correlation between crystal structure and enhanced microwave dielectric characteristics of wolframite-structure Mg0.5Zr0.5NbO4 ceramics

Abstract

An effective and simple synthesis of high-performance materials exerts a significant influence on low-cost commercial production with high production efficiency. In the present work, the effects of intrinsic factors on the microwave dielectric properties of reaction-sintering Mg0.5Zr0.5NbO4 ceramics were quantified through crystal chemistry, Raman analysis, and bond characteristics. Pure-phase and low-loss Mg0.5Zr0.5NbO4 ceramics were synthesized with an effective and simple reaction-sintering procedure. Detailed Raman vibrations with complete mode assignments were firstly investigated to characterize the lattice vibration. Rietveld refinement and Raman analysis confirmed the formation of pure-phase MgZrNb2O8 ceramics even with the reaction-sintering process. Moreover, well-distributed microstructure with enhanced densification (nearly full density) was verified through SEM and element mapping. Through the chemical bond theory, the dielectric constant was dominated by the Nb–O bond ionicity (fiNb-O). The Q × f was strongly related to the lattice energy (UNb–O) and bond energy (ENb-O) of the Nb–O bond, while the τf value was influenced by the coefficient of thermal expansion of the Mg–O bond (αMg-O), providing guidance for performance modification of Mg0.5Zr0.5NbO4 systems. Excellent microwave dielectric properties for the samples sintered at 1350 °C: εr = 28.6, Q × f = 82,000 GHz (7.1 GHz) and τf = −47 ppm/°C were obtained via the reaction sintering process, exhibiting enormous potential for industrial production.