Improved microwave dielectric properties and sintering behavior of LiZnPO4 ceramic by Ni2+-ion doping based on first-principle calculation and experiment

Abstract Theoretical calculation and experimental verification were performed to investigate the effect of Ni2+-ion substitution on the microstructure, sintering behavior, and microwave dielectric properties of LiZnPO4 ceramic. The crystal structure, electron density, formation energy, and vibration mode of the doped system were discussed on the basis of density functional theory. Samples were synthesized using the traditional solid-state reaction method and characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, network analysis, differentia-thermal and thermo-mechanical analyses, and Raman spectrometry. The substitution of Ni2+ ions to Zn2+ ions could modify the bond length, bond population, and electron distribution of ZnO4 tetrahedron. The vibration, microstructure, and sintering properties changed accordingly. The densification level and microwave dielectric properties improved ( e r =5.57, Q × f  = 63,951  GHz at 15 GHz, τ f  = -79.5 ppm/°C, relative density = 97.27%) when 4% (molar ratio) Zn2+ ions were replaced by Ni2+ ions sintered at 825 °C. The Ni2+-ion substitution could enhance the dielectric and sintering properties of LiZnPO4 ceramic.