High-temperature stability of ThMn12 magnet materials

Kurima Kobayashi, Daiki Furusawa, Shunji Suzuki, Tomoko Kuno, Kimiko Urushibata, Noritsugu Sakuma, Masao Yano, Tetsuya Shoji, Akira Kato, Akira Manabe, Satoshi Sugimoto

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

The nitrogenated alloys (Nd0.7Zr0.3)(Fe0.75Co0.25)11.5Ti0.5N1.3 (A) and Nd(Fe0.8Co0.2)11Mo1.0N1.0 (B) and the non-nitrogenated alloy (Sm0.8Zr0.2)(Fe0.75Co0.25)11.5Ti0.5 (C), having a ThMn12 structure, show interesting magnetic properties and are candidate materials for high-temperature magnets. In this study, the stability of these materials was studied using Curie temperature measurements, differential scanning calorimetry, differential thermal analysis, thermogravimetry from room temperature to 1573 K, and X-ray diffraction of treated samples. The nitrogenated samples (A) and (B) started to decompose into the ¡-(Fe, Co) phase and other X-ray amorphous phases from about 800 and 1000 K, respectively. Sample (C) exists as a metastable phase at room temperature and decomposed above 700 K at a relatively high oxygen partial pressure (PO2 > 10 Pa), but the ThMn12 structure remained up to at least 1373 K in an almost oxygen-free atmosphere (PO2 < 10115 Pa). Sample (C) is intrinsically stable at temperatures higher than about 1000 K up to the melting temperature, which was estimated to be 1480 K. The ThMn12 structure in both R = Nd and Sm starting alloys is metastable at room temperature, and becomes unstable under 8001000 K. The decomposition rate was clearly dependent on the PO2 in the heated atmosphere, as high PO2 led to sample oxidation, and on the sample composition.

Original languageEnglish
Pages (from-to)1845-1853
Number of pages9
JournalMaterials Transactions
Volume59
Issue number11
DOIs
Publication statusPublished - 2018 Jan 1

Keywords

  • 1-12 structure compounds
  • Differential scanning calorimetry analysis
  • Differential thermal analysis
  • High-temperature X-ray diffraction
  • High-temperature stability
  • Oxygen partial pressure
  • Polarization change by heating
  • Thermogravimetry analysis

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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