Microwave Dielectric Properties of MgZr1-x(HfTiSnGe)x/4Nb2O8 Ceramics via High Entropy Strategy

The wolframite structure high-entropy ceramic with chemical composition MgZr1-x(HfTiSnGe)x/4Nb2O8 was synthesized by the solid-state reaction method. The decrease in dielectric constant (εr) was mainly determined by polarizability, and this was further confirmed by the ionicity of the Nb-O bond. The quality factor (Qf) is affected by the lattice energy, the full width at half maximum (FWHM) at 285 cm⁻¹, and the structural strain. Compared with the substrate MgZrNb2O8 (58, 500 GHz), Qf has been significantly improved (106, 500 GHz). At the same time, the deterioration of the resonant frequency temperature coefficient (τf) caused by a single ion substitution has been avoided, and τf has reached -31 ppm/°C. The τf is closely related to the total bond valence and the tolerance factor. The high-entropy strategy has successfully reduced the ceramic loss and enhanced the temperature stability. The relationship between microwave dielectric properties and the structure was established.