Colossal permittivity and ultralow dielectric loss in Nb-doped SrTiO₃ ceramics

Defect engineering has been applied to prepare materials with modifiable dielectric properties. SrTiNb_xO₃ (x = 0, 0.003, 0.006, 0.009, 0.012) ceramics were synthesized using the traditional solid-state reaction method and sintered in a reducing atmosphere. All samples show excellent dielectric properties with giant permittivity (> 3.5×10⁴) and low dielectric loss (< 0.01). SrTiNb_0.003O₃ ceramic exhibits a colossal permittivity of 4.6×10⁴ and an ultralow dielectric loss of 0.005 (1 kHz, room temperature) as well as great temperature stability in the range of (−60)–160℃. The mechanism of the presented colossal permittivity (CP) properties is investigated by conducting X-ray photoelectron spectroscopy (XPS) and analyzing activation energies. The results indicate that the introduction of Nb⁵⁺ and the reducing sintering atmosphere together generated the formation of Ti³⁺ and ${\text{V}}_{\text{O}}^{··}$. These defects further form ${\text{Ti}}_{\text{Ti}}^{\prime }-{\text{V}}_{\text{O}}^{··}-{\text{Ti}}_{\text{Ti}}^{\prime }$ defect dipoles, contributing to the coexisting giant permittivity and low dielectric loss in Nb-doped SrTiO₃ (STN) ceramics.