Electrical conductivity anomaly and X-ray photoelectron spectroscopy investigation of YCr1−xMnxO3 negative temperature coefficient ceramics

Electrical conductivity anomaly of perovskite-type YCr1−xMnxO3 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 YCr1−xMnxO3 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.