Near-zero temperature coefficient in Mg2+-Ti4+ co-doped Sm2O3-CaSmAlO4 microwave dielectric ceramics

The practical application of CaSmAlO4 microwave dielectric ceramics is limited by its low quality factor (Qxf) value and non-zero temperature coefficient resonant frequency (tau(f)) value. In this study, we introduced Mg2+-Ti4+ ionic pairs into CaSmAlO4, along with an excess of 9% Sm2O3. The Mg2+-Ti4+ ionic pairs substituted Al3+, and two phases simultaneously coexisted in the ceramics: CaSmAlO4 and Sm2O3. As the doping concentration of Mg2+-Ti4+ ionic pairs increased, the relative permittivity exhibited an upward trend, while the quality factor and resonant frequency temperature coefficient first rose and then descended. Remarkably, 0.09Sm(2)O(3)-0.91CaSmAl(0.7)Mg(0.15)-Ti0.15O4 sintered at 1450 degrees C yielded excellent dielectric properties: epsilon(r) = 19.72, Q x f = 72,936 GHz, and tau(f) = -0.044 ppm<middle dot>degrees C- 1. The factors influencing the microwave dielectric properties of 0.09Sm(2)O(3)-0.91CaSmAlO(4) ceramics were further examined by considering the crystal structure, grain size, Lichtenecker logarithmic rule, tolerance factor and packing fraction.