Resolving the Role of Configurational Entropy in the Optimization of Mechanical, Thermal, and Microwave Dielectric Properties of SrLa(Al_{0.50–<i>x</i>}Ga_<i>x</i>Zn_0.125Mg_0.125Ti_0.25)O₄ C

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-<i>x</i>}Ga_<i>x</i>Zn_0.125Mg_0.125Ti_0.25)O₄ (<i>x</i> = 0-0.20) ceramics were designed by leveraging the unique properties of SrLaAlO₄ ceramics and high-entropy engineering. The effects of configurational entropy (<i>S</i>_conf = 1.23R - 1.54R) on the mechanical, thermal, and microwave dielectric properties of SrLa(Al_{0.50-<i>x</i>}Ga_<i>x</i>Zn_0.125Mg_0.125Ti_0.25)O₄ 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>I</i>4/<i>mmm</i>. Significant improvements in Vickers hardness were observed with increasing <i>S</i>_conf, reaching 8.05 GPa at <i>S</i>_conf = 1.54R compared to 5.64 GPa in SrLaAlO₄ 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 (<i>Q</i> × <i>f</i>) of 98,000 GHz was achieved at <i>S</i>_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, <i>Q × f</i> = 98,000 GHz, and τ_f = -2.0 ppm/°C were obtained at <i>S</i>_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.