Abstract
The drift in electrical properties (e. g., the resistivity and B-value) is vital to the practical application for negative temperature coefficient (NTC) ceramics. In this work, Cu-doped nickel manganite ceramics were prepared by solid-state method, to investigate the degradation mechanism of both the resistivity and B-value. Results showed that the as-prepared ceramics exhibited typical NTC characteristics with cubic spinel phase, and that Cu doping greatly reduced the resistivity and B-value. However, the increase of Cu content in system aggravated the drift in the resistivity and B-value after the samples were aged at 300 °C for 30 h. XPS was carried out to further clarify the change in electrical properties. It was found that the decline of properties was due to the decrease of Mn4+ content in system after aging, which derived from the increase of chemical valence of Cu.
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