Sintering behavior, structural evolution and microwave dielectric properties of Zn1.8SiO3.8-xMgF2 ceramics

Zn _1.8SiO _3.8- xMgF ₂ ceramics were synthesized using the conventional solid-state reaction method. The structural evolution of the ceramics was analyzed, and the influence of both intrinsic and extrinsic factors on their dielectric properties was discussed. The results show that Zn ₂SiO ₄ is the major phase in pure Zn _1.8SiO _3.8 ceramics, while the Si-rich amorphous phase is identified as the second phase. The addition of MgF ₂ induces a reaction between the Zn _1.8SiO _3.8 ceramic and MgF ₂, resulting in the transformation of the Zn ₂SiO ₄ phase into a solid solution containing Mg ²⁺ and F ^-, along with a reduction in the Si-rich phase. A dense microstructure is observed in the samples with x ≤ 2 wt%, whereas the samples with x ≥ 3 wt% exhibit a porous microstructure due to the disappearance of the liquid phase and the volatilization of F ^-. The dielectric constant ( ε _r) of the ceramics is primarily influenced by their density. Notably, MgF ₂ enhances the lattice energy and modifies the defect characteristics, reducing both intrinsic and extrinsic losses. In the range of x ≤ 2 wt%, the quality factor ( Qf) values of the ceramics increase with increasing x. However, the samples with x ≥ 3 wt% show extremely high dielectric loss due to their low density. Consequently, the samples with x = 2 wt% exhibit optimal dielectric properties, with a ε _r of 6.45, a Qf of 127,500 GHz, and a τ _f of −25.1 ppm/°C.