New SrSmGa₃O₇ Ceramics: Sintering Behavior, Structure, Electrical, and Microwave Dielectric Properties

The development of high-frequency communication technology urgently requires new types of microwave dielectric ceramics with excellent performance. New melilite-structured SrSmGa₃O₇ ceramics were prepared by using the conventional solid-state method. The impedance analysis demonstrates that SrSmGa₃O₇ ceramics have good insulation characteristics, with the conducting activation energies of 0.51 and 1.01 eV for the grain and grain boundary, respectively. The bond valence theory suggests that the stretched Sm-O and Ga-O bonds have a major influence on ε_r, leading to a higher measured value than the theoretical one (7.6). The calculation by P-V-L chemical bond theory shows that the Sr/Sm-O bond significantly affects the bond ionicity (<i>f</i>_i), and the Ga-O bonds have a crucial influence on the lattice energy (<i>U</i>_b) and bond energy (<i>E</i>_b). This result provides guidance for SrSmGa₃O₇ ceramic modification to enhance its performance. The 1425 °C sintered SrSmGa₃O₇ ceramic exhibited the optimal microwave dielectric properties (ε_r = 12.1 ± 0.1, <i>Q</i> × <i>f</i> = 27,740 ± 613 GHz (at 11.4 GHz), and τ_f = -37.5 ± 0.4 ppm/°C), indicating that the SrSmGa₃O₇ ceramics are a favorable dielectric material for high-frequency applications.