Phase-microstructure evolution and microwave dielectric characteristic of (1−x)(Sr0.5Ce0.5)TiO3+δ−xNdAlO3 solid solution

A perovskite solid solution (1−x)(Sr0.5Ce0.5)TiO3+δ−xNdAlO3, x = 0.1 to 0.4 was prepared by conventional solid state method. X-ray diffraction spectra revealed a single phase with tetragonal structure, indicating that doping of NdAlO3 significantly stabilized the perovskite-like structure. The addition of NdAlO3 facilitated the formation of large plate-like grains with porous microstructure. The dielectric constant (εr) decreased with increasing x because of the small ionic polarizability of NdAlO3. The Q × f value was strongly dependent on the microstructure of these ceramics. The temperature coefficient of resonant frequency (τf) gradually shifted to near zero with a rise of x, which resulted from the decrease in tolerance factor (t). The solid solution with x = 0.4 sintered at 1550 °C for 4 h showed a good combination of dielectric properties: εr = 72, Q × f = 12052 GHz and τf = +5 pmm/°C.