High sintering and dielectric performance: The improved (Mg, Zn)₃B₂O₆ ceramics with the help of the DFT calculation

With the help of the first principle calculation, the solid-state reaction experiment was conducted to investigate the alteration in the sintering and the microwave dielectric properties of Mg₃B₂O₆ ceramic with many Zn²⁺ substitutions. These properties were characterized using the scanning electron microscopy, network analyzer, X-ray diffraction, Raman spectroscopy, energy-dispersive spectroscopy, and thermomechanical and differential-thermal analyses. The coexistence of Mg₃B₂O₆, Mg₂B₂O₅ and ZnO ceramics could be observed with increasing Zn²⁺ addition, and the lattice distortion occurred in the Mg₂B₂O₅ and Mg₃B₂O₆ ceramics due to the substitution of Mg²⁺ with Zn²⁺. The electron density and the bond property of the MgO₆ octahedron changed, and a quantitative method was used to discuss the variation in sintering, substitution and phase formation properties. The densification window was decreased to 1100 °C, and the dielectric properties improved with the formation of a three-phase borate solid solution (dielectric constant = 6.73, quality factor = 112,000 GHz at 16 GHz (Q = 7000), temperature coefficient of resonant frequency = −61.2 ppm °C⁻¹, and relative density = 97.0%).