Resolving the Role of Configurational Entropy in the Optimization of Mechanical, Thermal, and Microwave Dielectric Properties of SrLa(Al_0.50–xGa_xZn_0.125Mg_0.125Ti_0.25)O₄ Ceramics

The demand for high-performance microwave dielectric ceramics has surged with the proliferation of fifth-generation (5G) communication networks. In this work, SrLa(Al 0.50– x Ga x Zn 0.125 Mg 0.125 Ti 0.25 )O 4 ( x = 0–0.20) ceramics were designed by leveraging the unique properties of SrLaAlO 4 ceramics and high-entropy engineering. The effects of configurational entropy ( S conf = 1.23R – 1.54R) on the mechanical, thermal, and microwave dielectric properties of SrLa(Al 0.50– x Ga x Zn 0.125 Mg 0.125 Ti 0.25 )O 4 ceramics were investigated. X-ray diffractometer and transmission electron microscope analyses confirmed that each composition belonged to the tetragonal structure with a space group of I 4/ mmm . Significant improvements in Vickers hardness were observed with increasing S conf, reaching 8.05 GPa at S conf = 1.54R compared to 5.64 GPa in SrLaAlO 4 ceramics. Additionally, the increasing entropy showed great potential in reducing the thermal expansion coefficient (CTE) from 12.32 to 11.49 ppm/°C. The optimal quality factor ( Q × f ) of 98,000 GHz was achieved at S conf = 1.37R, attributed to the optimization of intrinsic lattice energy and infrared-damped modes. The temperature coefficient of resonant frequency (τ f ) was successfully modified toward zero due to entropy-driven CTE and structural modifications. Excellent microwave dielectric properties with ε r = 22.5, Q × f = 98,000 GHz, and τ f = −2.0 ppm/°C were obtained at S conf = 1.37R. This work highlights the potential of entropy-engineering in developing high-performance microwave dielectric ceramics, offering a promising pathway for the advancement of 5G communication components.