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<p>Ni<sub>0.6−<i>x</i></sub>Mn<sub>1.8</sub>Co<sub>0.6</sub>Cu<sub><i>x</i></sub>O<sub>4</sub> (0 ≤ <i>x</i> ≤ 0.25) ceramics were synthesized via the solid-state reaction method. The effects of Cu doping content on phase structure, cation valence state, impedance characteristic, electrical performance and long-term thermal stability were investigated systematically. Rietveld refinement analyses demonstrate that the fraction of the tetragonal spinel phase increases with the elevation of Cu doping content. All as-fabricated ceramics exhibit typical negative temperature coefficient thermosensitive behaviors. Cu doping allows for the precise adjustment of variable-valence cation levels and oxygen vacancy densities in the ceramic matrix, resulting in an optimal balance of low electrical resistivity and a high material constant (<i>B</i> value). For 0.1 ≤ <i>x</i> ≤ 0.2, all samples exhibit <i>ρ</i><sub>25</sub> under 100 Ω cm, a <i>B</i><sub>25/50</sub> value over 3200&#xa0;K. The resistance drift rate (Δ<i>R</i>/<i>R</i><sub>0</sub>) below 3% after 200&#xa0;h of aging, and less than 6% after 500&#xa0;h of aging. The primary electrical conduction mechanism involves small polaron hopping between transition metal cations and oxygen vacancy grain boundary migration. This study elucidates how Cu doping influences the microstructure and cation valence state distribution in ceramics, offering a straightforward strategy for designing high-performance NTC ceramics with low resistivity and high <i>B</i> value.</p>

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Cu doped Ni0.6−xMn1.8Co0.6CuxO4 ceramics with controllable electrical properties for low resistivity and high B value NTC thermistors

  • 期刊论文

  • 发表日期：

    2026年5月19日

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  • Zhen Zhang,
  • Zhumiao Wang,
  • Yunfei Liu,
  • Yinong Lyu

摘要

Ni0.6−xMn1.8Co0.6CuxO4 (0 ≤ x ≤ 0.25) ceramics were synthesized via the solid-state reaction method. The effects of Cu doping content on phase structure, cation valence state, impedance characteristic, electrical performance and long-term thermal stability were investigated systematically. Rietveld refinement analyses demonstrate that the fraction of the tetragonal spinel phase increases with the elevation of Cu doping content. All as-fabricated ceramics exhibit typical negative temperature coefficient thermosensitive behaviors. Cu doping allows for the precise adjustment of variable-valence cation levels and oxygen vacancy densities in the ceramic matrix, resulting in an optimal balance of low electrical resistivity and a high material constant (B value). For 0.1 ≤ x ≤ 0.2, all samples exhibit ρ25 under 100 Ω cm, a B25/50 value over 3200 K. The resistance drift rate (ΔR/R0) below 3% after 200 h of aging, and less than 6% after 500 h of aging. The primary electrical conduction mechanism involves small polaron hopping between transition metal cations and oxygen vacancy grain boundary migration. This study elucidates how Cu doping influences the microstructure and cation valence state distribution in ceramics, offering a straightforward strategy for designing high-performance NTC ceramics with low resistivity and high B value.