Structural characterizations, dielectric properties and impedance spectroscopy analysis of Nd _x Sr_1-1.5x TiO₃ ceramics

The Nd _x Sr_1–1.5x TiO₃ ceramics (x = 0, 0.008, 0.024, 0.056, 0.104, 0.152 and 0.200) were prepared by solid state reaction method. X-ray diffraction (XRD) results indicated pure perovskite phase for all ceramics and the structure changed from cubic to tetragonal by increasing x value. Scanning electron microscopy (SEM) images showed high dense microstructure for all ceramics, and the grain size was strongly suppressed to ~1 μm for Nd _x Sr_1–1.5x TiO₃ ceramics with x = 0.008, then gradually increased by further increasing x value and reached ~10 μm when x = 0.200. The relative dielectric constant ε _r was strongly enhanced to 5,060 for the sample with x = 0.024, while its dielectric loss tanδ was still lower than 0.03. Together with its relatively high breakdown strength E _b > 10 kV/mm, this ceramic should be a good candidate for high-voltage capacitor applications with enhanced energy storage densities. Impedance spectroscopy analysis revealed that the Nd _x Sr_1–1.5x TiO₃ ceramics showed electrically heterogeneous, and the space charge polarization at interfaces should contribute to the observed high dielectric constant ε _r.