Electrical conductivity anomaly and X-ray photoelectron spectroscopy investigation of YCr_1−xMn_xO₃ negative temperature coefficient ceramics

Electrical conductivity anomaly of perovskite-type YCr_1−xMn_xO₃ negative temperature coefficient (NTC) ceramics produced by spark plasma sintering (SPS) has been investigated by using defect chemistry theory combination with X-ray photoelectron spectroscopy (XPS) analysis. From the results of the lnρ-1/T curves and the XPS analysis, it can be considered that YCr_1−xMn_xO₃ ceramics exhibit the hopping conductivity. The major carriers in YCrO₃ are holes, which are compensated by the oxygen vacancies produced due to the introduction of Mn ions. The Mn⁴⁺ ion contents increase monotonically in the range of 0.2 ≤ x ≤ 0.5. The resistivity increases at first and then decreases with increasing Mn contents, which has the same varying tendency with activation energy. The electrical conductivity anomaly appearing in these ceramics may be due to the variation of Cr⁴⁺ and Mn⁴⁺ ions concentration as Mn content changes.