Structure and microwave dielectric properties of Al3+-doped (Zn1/6Ba1/6Ca1/6Sr1/6La1/3)TiO3 high-entropy ceramics system

In this study, based on the highly disordered multi-component system with high-entropy and traditional perovskite with high dielectric constant, a series of the Al3+-doped high-entropy perovskite (Zn1/6Ba1/6Ca1/6Sr1/6La1/3)Ti1-xAlxO3 (0 ≤ x ≤ 0.1) ceramics was designed and synthesized by using a solid state reaction method to explore the effects of different doping amounts on microwave dielectric characteristics together with the microstructures. The single-phase structure in space group Pm-3m was determined in the sintering temperature range of 1325 °C–1400 °C and both had high dielectric constant (from 74.46 to 93.44). With the increase of Al doping amount, the variation trend of dielectric constant was closely related to the density and ionic polarizability. The Q × f value of doped samples was higher than that of undoped samples, which was mainly due to the interaction of oxygen vacancy content and grain size. Due to the high-entropy effect resulting in [Ti-O6] octahedral torsion, the τf value was greatly reduced compared with traditional perovskite, which exhibited outstanding microwave dielectric properties (εr = 74.46, Q × f = 4108 GHz at 4.31 GHz, and τf = +184 ppm/°C). The present work provided an effective approach to improve the properties of microwave dielectric ceramics.