Low-Temperature Iodine Heat Treatment of Quasi-One-Dimensional KFeS 2 Crystals

Hisao Kuriyaki, Kiichiro Takenaka

Research output: Contribution to journalArticle

Abstract

Low-temperature iodine heat treatment of quasi-one-dimensional KFeS 2 crystals was carried out. The resistivity along the c-axis is seen to decrease rapidly with increasing iodine-heat-treatment temperature and the nonmetallic temperature dependence was found to become weaker. The fluctuation-induced tunneling model was used to explain the reduction of the potential barrier at grain boundaries caused by the iodine heat treatment. In particular, samples subjected to iodine heat treatment at 100°C for 2 days exhibited a low room-temperature resistivity of approximately 10-1 Ωcm and a corresponding positive temperature gradient, which are evidence of the first observation of metallic behavior. Furthermore, the room-temperature Seebeck coefficient of these iodine-heat-treated samples was small, a value of +5.8 μV/K, and exhibited an almost linear temperature dependence that showed the samples to be metallic. Finally, although KFeS2 normally exhibits metallic conduction, the presence of grain boundaries formed during crystallization from the molten state is thought to have led to the nonmetallic conductivity observed in our experiments.

Original languageEnglish
Pages (from-to)188-191
Number of pages4
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Volume43
Issue number1
DOIs
Publication statusPublished - Jan 1 2004

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Iodine
iodine
heat treatment
Heat treatment
Crystals
crystals
Temperature
grain boundaries
Grain boundaries
temperature dependence
electrical resistivity
room temperature
Seebeck effect
Seebeck coefficient
temperature gradients
Thermal gradients
Molten materials
crystallization
conduction
Crystallization

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physics and Astronomy(all)

Cite this

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title = "Low-Temperature Iodine Heat Treatment of Quasi-One-Dimensional KFeS 2 Crystals",
abstract = "Low-temperature iodine heat treatment of quasi-one-dimensional KFeS 2 crystals was carried out. The resistivity along the c-axis is seen to decrease rapidly with increasing iodine-heat-treatment temperature and the nonmetallic temperature dependence was found to become weaker. The fluctuation-induced tunneling model was used to explain the reduction of the potential barrier at grain boundaries caused by the iodine heat treatment. In particular, samples subjected to iodine heat treatment at 100°C for 2 days exhibited a low room-temperature resistivity of approximately 10-1 Ωcm and a corresponding positive temperature gradient, which are evidence of the first observation of metallic behavior. Furthermore, the room-temperature Seebeck coefficient of these iodine-heat-treated samples was small, a value of +5.8 μV/K, and exhibited an almost linear temperature dependence that showed the samples to be metallic. Finally, although KFeS2 normally exhibits metallic conduction, the presence of grain boundaries formed during crystallization from the molten state is thought to have led to the nonmetallic conductivity observed in our experiments.",
author = "Hisao Kuriyaki and Kiichiro Takenaka",
year = "2004",
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N2 - Low-temperature iodine heat treatment of quasi-one-dimensional KFeS 2 crystals was carried out. The resistivity along the c-axis is seen to decrease rapidly with increasing iodine-heat-treatment temperature and the nonmetallic temperature dependence was found to become weaker. The fluctuation-induced tunneling model was used to explain the reduction of the potential barrier at grain boundaries caused by the iodine heat treatment. In particular, samples subjected to iodine heat treatment at 100°C for 2 days exhibited a low room-temperature resistivity of approximately 10-1 Ωcm and a corresponding positive temperature gradient, which are evidence of the first observation of metallic behavior. Furthermore, the room-temperature Seebeck coefficient of these iodine-heat-treated samples was small, a value of +5.8 μV/K, and exhibited an almost linear temperature dependence that showed the samples to be metallic. Finally, although KFeS2 normally exhibits metallic conduction, the presence of grain boundaries formed during crystallization from the molten state is thought to have led to the nonmetallic conductivity observed in our experiments.

AB - Low-temperature iodine heat treatment of quasi-one-dimensional KFeS 2 crystals was carried out. The resistivity along the c-axis is seen to decrease rapidly with increasing iodine-heat-treatment temperature and the nonmetallic temperature dependence was found to become weaker. The fluctuation-induced tunneling model was used to explain the reduction of the potential barrier at grain boundaries caused by the iodine heat treatment. In particular, samples subjected to iodine heat treatment at 100°C for 2 days exhibited a low room-temperature resistivity of approximately 10-1 Ωcm and a corresponding positive temperature gradient, which are evidence of the first observation of metallic behavior. Furthermore, the room-temperature Seebeck coefficient of these iodine-heat-treated samples was small, a value of +5.8 μV/K, and exhibited an almost linear temperature dependence that showed the samples to be metallic. Finally, although KFeS2 normally exhibits metallic conduction, the presence of grain boundaries formed during crystallization from the molten state is thought to have led to the nonmetallic conductivity observed in our experiments.

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