Microwave dielectric properties of 0.7(SryCa1-y)TiO3-0.3(SmxNd1-x)AlO3 ceramics with near-zero temperature coefficient

The microstructures and the microwave dielectric properties of 0.7(SryCa1-y)TiO3-0.3(SmxNd1-x)AlO3 (7SCT-3SNA) ceramics system prepared by conventional solid-state route were investigated. X-ray powder diffraction results showed solid solutions with the perovskite structure were completely formed within the entire observation x range, and the unit cell volume of 0.7CaTiO(3)-0.3(SmxNd1-x)AlO3 (7CT-3SNA) ceramics decreased with increasing x value. The substitution of Nd3+ by Sm3+ could enhance the densification of 7CT-3SNA ceramics, and consequently improve the dielectric properties of the ceramics. When x = 0.75, specimens exhibited excellent microwave dielectric properties with epsilon (r) similar to 44.52, Q x f value similar to 40,110 and tau (f) value similar to-1 ppm/A degrees C. For further improving the microwave dielectric properties of the samples, Ca2+ in 0.7CaTiO(3)-0.3(SmxNd1-x)AlO3 were partially substituted by Sr2+. The results showed that the replacement of Ca2+ by Sr2+ effectively enhanced the densification of specimens. By optimizing the composition, the ceramics with y = 0.01 in 0.7(SryCa1-y)TiO3-0.3(Sm0.75Nd0.25)AlO3 (7SCT-3SNA) showed high relative density and dense and uniform microstructures as well as well-developed grain growth with superior microwave dielectric properties: epsilon (r) similar to 45.38, Q x f value similar to 41,730 and tau (f) value similar to-0.2 ppm/A degrees C.