Appearance of remarkable PTCR characteristics of ZnO-TiO2-NiO ceramics prepared by spark plasma sintering method

Noboru Shikatani, Eishi Maeda, Masahiro Komatsu, Yukio Watanabe

研究成果: Contribution to journalArticle査読

抄録

We have prepared 85ZnO-10TiO2-5NiO ceramics by the spark plasma sintering (SPS) method aiming at appearance of remarkable increase in positive temperature coefficient of resistivity (PTCR). The specimens are found to have microstructures composed of small grains and neck-contacts. The PTCR characteristic is obtained when the specimens are oxidized by annealing over about 33 hours at 900°C, and becomes remarkable when the characteristic is measured in a reducing atmosphere of N2 gas. Especially for annealing during about 75 hours, the resistivity in the N2 atmosphere is found to increase markedly in a temperature range over 260°C, resulting in a peak value of 1.5 × 102Ωcm at about 380°C large by 3.5 order of magnitude compared to about 0.04Ωcm in a temperature range below the Curie point of 260°C. In order to study mechanisms by which such remarkable PTCR is observed, we have measured Seebeck coefficients of specimens. When the specimens are annealed, space-charge-layers are formed around the surfaces of neck-channels between grains by trapping of carrier electrons due to absorption of oxygens to ZnO and TiO2, which are N-type semiconductors. Thickness of the space-charge-layers increases with annealing time. Such growth of layers results in narrowing the parts of channels through which electrons flow, that is, in enhancing the PTCR.

本文言語英語
ページ(範囲)581-587
ページ数7
ジャーナルFuntai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy
49
7
DOI
出版ステータス出版済み - 7 2002
外部発表はい

All Science Journal Classification (ASJC) codes

  • Mechanical Engineering
  • Industrial and Manufacturing Engineering
  • Metals and Alloys
  • Materials Chemistry

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