Enhanced permittivity of Lu-doped SrTiO3 ceramics sintered in air atmosphere through defect chemistry

A series of Sr1‒1.5xLuxTiO3 (x = 0, 0.005, 0.01, 0.015, and 0.02) ceramics was sintered under an air atmosphere through the solid-state reaction method. The results show that doping with Lu3+ considerably enhances material permittivity. The ceramic with x = 0.01 exhibits a colossal permittivity (CP) of ∼101000 with a tanδ of ∼0.16 at a frequency of 1 kHz, demonstrating enhanced stability over a wide temperature (30 to 300 °C) and frequency (102 to 106 Hz) range. Based on the analysis of dielectric relaxation, X-ray photoelectron spectroscopy (XPS), and the universal dielectric response law, the CP effect is primarily due to the formation of defect dipoles, which are correlated with the presence of oxygen vacancies, such as Ti3+ Ti3+, , Ti3+, and Ti3+. These defect dipoles serve to pin electrons, limiting long-range transitions, and enhancing local polarization. Doping with Lu3+ also induces a secondary Lu2Ti2O7 phase, which are characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The results generated in this study can inform the development and application of new CP materials based on SrTiO3.