Novel non-equimolar SrLa(Al0.25Zn0.125Mg0.125Ga0.25Ti0.25)O4 high-entropy ceramics with excellent mechanical and microwave dielectric properties

Novel non-equimolar high-entropy SrLa(Al 0.25 Zn 0.125 Mg 0.125 Ti 0.25 Ga 0.25 )O 4 (SLAZMTG) ceramics with a layered perovskite structure have been prepared via the standard solid-state reaction method. The high-entropy composition belongs to the tetrahedral structure with a space group of I 4/ mmm , which is confirmed by the XRD and TEM analyses. Excellent microwave dielectric properties with a suitable dielectric constant ( ε r = 22.5), high quality factor ( Qf = 83,003 GHz), and near-zero τ f value of −1.7 ppm/°C are obtained in SLAZMTG ceramics sintered at 1400 °C. Meanwhile, a significant enhancement in compressive strength was achieved due to the improvement of configuration entropy, 912 MPa for SLAZMTG compared to 578 MPa in the pure SrLaAlO 4 composition. Additionally, the high-entropy engineering in the present work suggests great potential in achieving low thermal conductivities . SLAZMTG ceramics exhibit low thermal conductivities ranging from 2.86 W/m•K at 323 K to 1.99 W/m•K at 673 K, much lower than those of SrLaAlO 4 and other perovskite ceramics.