Structure and properties of (Mg_0.4Zn_0.6)₂SiO₄ microwave dielectric ceramics based on first-principles calculations

Mg₂SiO₄, the most studied low dielectric microwave ceramic system, has a dielectric constant that is too large compared to the demand. Compounding a low dielectric second phase and introducing a porous phase can reduce the dielectric constant. However, both methods often require a change in ceramics production technology routes. This paper attempts to reduce the dielectric constant of Mg₂SiO₄ using substitutional doping guided by theoretical calculations. Firstly, the substitution of zinc ions for magnesium ions was designed using first-principles calculations. Theoretical calculations show that Zn-O covalent bonding is more predominant after Zn²⁺ substitution and contributes most of the covalent bonding in the crystal cell, effectively weakening the ionic polarization in the structure and decreasing the dielectric constant of the ceramics. Secondly, the (Mg_0.4Zn_0.6)₂SiO₄ ration design was experimentally verified, and the sol-gel-molten salt method was used to reduce the ceramic sintering temperature in the experiments. Compared to the solid-phase methods, the sol-gel-molten salt method reduced ceramic sintering temperature to 1225 °C, while Zn²⁺ substitutional doping reduced the dielectric constant by 6.11.