Effects of composition tailoring on structure and microwave dielectric characteristics of SrSmAlO4 ceramics

Effects of composition tailoring on the microwave dielectric characteristics of SrSmAlO4 ceramics were investigated together with the structure. K2NiF4-type major phase with minor amount of secondary phases was observed in the modified ceramics with nominal composition Sr1+xSm1−xAlO4−x/2 (x = −0.05, −0.025, 0.025, 0.05), and the type of secondary phase is dependent on x. Sr2.25Sm0.75AlO4.875 secondary phase is detected for x > 0, while the secondary phase for x < 0 is SrSm2Al2O7. Though the accurate stoichiometric composition is very important to guarantee the highest Qf value, it is an effective way to adjust the temperature coefficient of resonant frequency τf by tailoring composition. τf can be adjusted from negative to positive by varying x from 0 to −0.05, while more negative τf can be achieved by varying x from 0 to 0.05. Suitable modified composition with x < 0 is also desired for obtaining high Qf value and small τf with the controlled sensitivity to sintering temperature.