Structure-dielectric property relations in (Al0.5Nb0.5)4+ co-doped Ca0.8Sr0.2TiO3 ceramics with excellent temperature stability

Ca0.8Sr0.2Ti1-x(Al0.5Nb0.5)xO3 (abbreviated as CSTANx) microwave dielectric ceramics were synthesized through the solid-state reaction. The effects of (Al0.5Nb0.5)4+ co-doping on the microstructure and dielectric behavior were systematically investigated, and the relationship between structure and property was discussed. All compositions exhibited a single orthorhombic phase with dense morphology. The doping of (Al0.5Nb0.5)4+ was beneficial to increasing the ordering at the B-site and inhibiting the reduction of Ti4+, which in turn reduced the dielectric loss. In addition, the temperature stability of relative permittivity and resonant frequency was significantly improved due to the limitation of relative permittivity as well as the distortion and tilting of BO6 octahedron. At 1 MHz, the variation of the relative permittivity (εr) for x = 0.6 composition was only 1% from 25 to 350 °C, and the loss angle tangent (tanδ) was below 0.003. Also, the x = 0.6 composition had the optimum microwave dielectric properties (εr = 45.7, Qf = 24,930 GHz, τf = + 3.1 ppm/°C). The results reveal that CSTAN0.6 ceramics can be used for communication devices such as resonators and filters.