Improvement of microwave dielectric characteristics in SrNdAlO4 ceramics by Ca-substitution

Single-phase (Sr1−xCax)NdAlO4 (x=0, 0.2, 0.4, 0.6, 0.8, and 1) solid solutions with K2NiF4-type structure were obtained by a standard solid-state reaction approach in the entire composition range. The microwave dielectric characteristics of SrNdAlO4 were significantly modified by Ca-substitution. With increasing x, the dielectric constant εr increased slightly; the temperature coefficient of resonant frequency τf could be adjusted from −16.5 ppm/°C to −11.5 ppm/°C. The significantly improved Qf value was achieved in the present ceramics with increasing x and reached the maximum, and then it decreased. The best combination of microwave dielectric characteristics was achieved at x=0.6: εr=18.9, Qf=91,300 GHz, τf=−12.9 ppm/°C.