Improved high-frequency properties of LiMgPO₄ ceramics by V⁵⁺ ion doping and first-principles calculations

The effects of V⁵⁺ ion substitution on the sintering behavior, microstructure, and high-frequency properties of LiMgPO₄ ceramics were investigated through theoretical calculations and experimental verification. The geometrical models before and after substitution were established and the structures were optimized to finally obtain the energy band structure, deformation charge density, and elastic constant of the samples based on first-principles calculations. Samples were prepared using solid-phase method and characterized using X-ray diffraction, scanning electron microscopy, and network analysis. Calculations show that the cell parameters and elastic modulus increase while the forbidden band width decreases through the substitution of V⁵⁺ ions for P⁵⁺ ions, which increases the electronic interactions between V and the surrounding atoms and improves the stability of the structure. The experimental results show that the substitution of V⁵⁺ ions indeed enhances the structural stability and improves the high-frequency performance of LiMgPO₄ ceramics. Among the specimens, LiMg(P_0.98V_0.02)O₄ ceramics sintered at 950°C showed better performance with ρ_r = 96.37%, ε_r = 6.82, and tanδ = 1.58 × 10^-3.