Anti-occupation defect dipole and gradient interface induced excellent giant permittivity in Sr_0.95Bi_0.05TiO₃ ceramics

In this research, non-stoichiometric Bi doped SrTiO3 (ST) ceramics with nominal chemical formula of BixSr1-xTiO3 (x = 0, 0.01, 0.03, 0.05, 0.07) were produced through a conventional solid-state reaction route. A giant permittivity (epsilon) similar to 30000 and low dielectric loss (tan delta) similar to 0.03 were obtained in Bi0.05Sr0.95TiO3 ceramic. The temperature-epsilon and frequency-epsilon plots were conducted to investigate dielectric properties of the ceramics. The results of dielectric property plots revealed that the Bi0.05Sr0.95TiO3 ceramic has excellent dielectric stability within the range of 10(3)-10(6) Hz and 30-250 degree celsius. The fine scan XRD analysis, X-ray photoelectron spectrometer (XPS) and first principles calculation results showed that giant permittivity property of the Bi0.05Sr0.95TiO3 ceramic maybe attributed to the Bi-Ti' - V-O(center dot center dot) - Bi-Ti' defect dipoles caused by Bi anti -occupation doping. And the gradient interface formed by Bi excessive doping also contributed to the giant permittivity. This study offers a new approach for achieving a giant permittivity with low dielectric loss in ST ceramic capacitors.