Effects of O2 and N2 sintering atmospheres on electric properties of 0.9SrTiO3–0.1NiFe2O4 composite ceramics

Abstract The 0.9SrTiO3–0.1NiFe2O4 (STO/NFO) composite ceramics sintered at O2/N2 atmospheres were investigated. The N2-sintered STO/NFO (STO/NFON) had a larger microstrain (0.092(47)%) than the O2-sintered STO/NFO (STO/NFOO) revealed by the Rietveld refinement and the Williamson-Hall analysis. The maximum polarization of STO/NFON increased to ~7.1 μC/cm2, but the larger leakage current in STO/NFOO resulted in a 20% larger false remanent polarization value. Moreover, STO/NFON presented a lower activation energy (Ea, 1.22 eV), which implied more oxygen vacancies ( V O ⋅ ⋅ ). The amount of Ti3+ ions (60%) in STO/NFON increased as well, which formed defect dipoles [Ti4+·e− V O ⋅ ⋅ −Ti4+·e] and fixed V O ⋅ ⋅ . The composite of STO/NFON also showed decreased V O ⋅ ⋅ content (~53%) owing to the fixing effect and presented low leakage current, increased impedances, and the improved ferroelectric hysteresis loop. The anomaly dielectric constants peaks indicated different conductivity mechanisms related to V O ⋅ ⋅ , and the STO/NFON ceramic possessed a low rate of dielectric loss.