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 Bi_xSr_1-xTiO₃ (x = 0, 0.01, 0.03, 0.05, 0.07) were produced through a conventional solid-state reaction route. A giant permittivity (ε) ∼30000 and low dielectric loss (tanδ) ∼0.03 were obtained in Bi_0.05Sr_0.95TiO₃ ceramic. The temperature-ε and frequency-ε plots were conducted to investigate dielectric properties of the ceramics. The results of dielectric property plots revealed that the Bi_0.05Sr_0.95TiO₃ ceramic has excellent dielectric stability within the range of 10³–10⁶ Hz and 30–250 °C. The fine scan XRD analysis, X-ray photoelectron spectrometer (XPS) and first principles calculation results showed that giant permittivity property of the Bi_0.05Sr_0.95TiO₃ ceramic maybe attributed to the Bi‘_Ti−V_O^∙∙−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.