Preparation of (Ba0.25Ca0.25Sr0.25La0.25)Ti1-xAlxO3 High-Entropy Perovskite Ceramics for enhanced Microwave Dielectric Performance

Development of microwave dielectric ceramics with a high dielectric constant, high quality factor, and low temperature coefficient of resonant frequency is of great importance for achieving miniaturization, low loss, and high stability in microwave devices. Research on low dielectric constant microwave dielectric ceramics has made certain progress, but the development of new systems of high dielectric constant microwave dielectric ceramics with excellent overall performance is still in the exploratory stage. Herein, approaches of high-entropy strategy and small radius ions doping were combined to achieve high microwave dielectric properties. It is demonstrated that a high-entropy ceramic with a perovskite structure doped with Al³⁺ ion, denoted as (Ba_0.25Ca_0.25Sr_0.25La_0.25)Ti_1-xAl_xO₃ (abbreviated as HESOs, 0<x≤0.25), was successfully synthesized. At x=0.1 and 1500 ^oC, HESO exhibited optimized comprehensive dielectric performance, characterized by ε_r = 89.25, Q×f = 3304 GHz, and τ_f = +361 ppm_/^oC. Besides, as the aluminum ion content increases, there is a reduction in grain size accompanied by an elevation in oxygen vacancy content, resulting in increase of Q×f, with a peak value reaching 4136 GHz. This study presents a valuable exploration aimed at designing high-entropy perovskite ceramics with excellent dielectric properties.