Colossal permittivity in Ta-doped SrTiO3 ceramics induced by interface effects and defect structure: An experimental and theoretical study

Abstract

The lack of systematic research on the phase structure, defect structure, and polarization mechanism hinders the full comprehension of the colossal permittivity (CP) behavior for SrTiO3-based ceramics. For this purpose, Ta-doped SrTiO3-based ceramics were synthesized in an N2 atmosphere with a traditional method. When the appropriate amount of Ta was doped, colossal permittivity (ԑr ∼ 62505), low dielectric loss (tanδ ∼ 0.07), as well as excellent temperature stability (−70 °C–180 °C, ΔC/C25°C ≤ ±15%) were obtained in the Sr0.996Ta0.004TiO3 ceramic. The relationship between Ta doping, polarization mechanism, and dielectric performance was systematically researched according to experimental analysis and theoretical calculations. The first-principle calculations indicate that the Ta5+ ion prefers to replace the Sr-site. The defect dipoles and oxygen vacancies formed by heterogeneous-ion doping play an active role in regulating the dielectric performance of ceramics. In addition, the interface barrier layer capacitance (IBLC) effect associated with semi-conductive grains and insulating grain boundaries is the primary origin of colossal permittivity for Sr1-xTaxTiO3 ceramics. The polarization mechanism and defect structure proposed in the study can be extended to the research of SrTiO3 CP ceramics. The results have a good development prospect in colossal permittivity (CP) materials.