Structural and thermal properties of ternary narrow-gap oxide semiconductor; Wurtzite-derived β-CuGaO2

Hiraku Nagatani, Issei Suzuki, Masao Kita, Masahiko Tanaka, Yoshio Katsuya, Osami Sakata, Shogo Miyoshi, Shu Yamaguchi, Takahisa Omata

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29 Citations (Scopus)


The crystal structure of the wurtzite-derived β-CuGaO2 was refined by Rietveld analysis of high-resolution powder diffraction data obtained from synchrotron X-ray radiation. Its structural characteristics are discussed in comparison with the other I-III-VI2 and II-VI oxide semiconductors. The cation and oxygen tetrahedral distortions of the β-CuGaO2 from an ideal wurtzite structure are small. The direct band-gap nature of the β-CuGaO2, unlike β-Ag(Ga,Al)O2, was explained by small cation and oxygen tetrahedral distortions. In terms of the thermal stability, the β-CuGaO2 irreversibly transforms into delafossite α-CuGaO2 at >460 °C in an Ar atmosphere. The transformation enthalpy was approximately -32 kJ mol-1, from differential scanning calorimetry. This value is close to the transformation enthalpy of CoO from the metastable zincblende form to the stable rock-salt form. The monovalent copper in β-CuGaO2 was oxidized to divalent copper in an oxygen atmosphere and transformed into a mixture of CuGa2O4 spinel and CuO at temperatures >350°C. These thermal properties indicate that β-CuGaO2 is stable at ≤300°C in both reducing and oxidizing atmospheres while in its metastable form. Consequently, this material could be of use in optoelectronic devices that do not exceed 300°C.

Original languageEnglish
Pages (from-to)1698-1704
Number of pages7
JournalInorganic chemistry
Issue number4
Publication statusPublished - 2015 Feb 16
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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