Enhanced dielectric properties and chemical bond characteristics of MgNb2O6 ceramics due to magnesium oxide doping

Abstract

Herein, the effects of MgO doping on the crystal structure, microstructure, chemical bond properties, vibrational properties and microwave dielectric performances of MgNb2O6 + x mol% MgO (x = 0–3) ceramics fabricated by solid-state reaction were examined. The results show that the doping of MgO does not produce a second phase and Mg2+ ions enter the lattice to form a continuous solid solution. The Q×f value of the system increases from 112,630 GHz (x = 0) to 121,580 GHz (x = 1), which is due to the microstructure and FWHM. In addition, the dielectric constant of ceramics is mainly influenced by the bond ionicity of Nb–O bond, relative density, and porosity. Meanwhile, the τf value shifts in the negative direction due to the variations of bond energy for Nb–O bond, bond valence of Nb–O bond, thermal expansion coefficient of Nb–O bond, and NbO6 octahedral distortion. The MgNb2O6 + 1 mol% MgO ceramics sintered at 1460 °C exhibit amazing microwave dielectric properties (εr = 20.82, Q ×f = 121,580 GHz, and τf = −48.89 ppm/°C), providing a potential candidate for modern microwave communications.