Effects of Sm₂O₃/SrO/LiF doping and cooling rate on sintering characteristics and microwave dielectric properties of (Zr_0.8Sn_0.2)TiO₄ ceramics

The present study aims to synthesize (Zr_0.8Sn_0.2)TiO₄ (ZST) ceramics and determine the optimum content of Sm₂O₃/SrO/LiF doping and cooling rate to improve processing and microwave dielectric properties of the ceramics. The initial content of three additives was preliminarily determined by analyzing the phase composition, microstructure, sintering characteristics and microwave dielectric performance of ZST ceramics samples. As a typical fluxing agent, the optimum LiF content was further explored, and the effects of different LiF contents on 0.8 wt% Sm₂O₃ + 0.4 wt% SrO doped ceramics were investigated. A suitable amount of liquid phase could be formed at a lower temperature when adding suitable LiF content into ceramics. The results showed the 0.3 wt% LiF not only promoted densification process but also reduced the sintering temperature to 1285 °C, which made the dielectric properties better. Moreover, the cooling rate also affected the performance of ZST ceramics, and the optimum cooling rate was determined through analyzing the lattice parameters and microstructure. Comparing the comprehensive properties of various ZST ceramics doped with 0.8 wt% Sm₂O₃ + 0.4 wt% SrO + 0.3 wt% LiF, the ceramic exhibited the densest microstructure and the best dielectric performance where ε_r = 39.66, Q × f = 45,150 GHz (f = 5.6 GHz), and τ_f = − 4.88 ppm/°C when the cooling rate was 1 °C/min and the sintering temperature was 1285 °C.