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

The practical application of CaSmAlO 4 microwave dielectric ceramics is limited by its low quality factor ( Q × f ) value and non-zero temperature coefficient resonant frequency ( τ f ) value. In this study, we introduced Mg 2+ –Ti 4+ ionic pairs into CaSmAlO 4 , along with an excess of 9% Sm 2 O 3 . The Mg 2+ –Ti 4+ ionic pairs substituted Al 3+ , and two phases simultaneously coexisted in the ceramics: CaSmAlO 4 and Sm 2 O 3 . As the doping concentration of Mg 2+ –Ti 4+ 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 –Ti 0.15 O 4 sintered at 1450 °C yielded excellent dielectric properties: ε r  = 19.72, Q  ×  f  = 72,936 GHz, and τ f  = –0.044 ppm·°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. Graphic abstract