Thermal behavior of modulated haüyne from Eifel, Germany: In situ high–temperature single–crystal X–ray diffraction study

Abstract

In–situ high–temperature single–crystal X–ray diffraction experiments on modulated haüyne obtained from Eifel, Germany, were conducted to re–evaluate its thermal behavior. The linearity of its thermal expansion is lost between 600 and 700 °C. Satellite peaks, indicating the modulated structure, were clearly observed up to 600 °C, but disappeared at 700 °C. These results indicate that the modulated haüyne structure changed in this temperature region. In addition, according to the observation of X–ray oscillation images taken at ambient conditions, the modulated structure of the sample heat–treated below 1000 °C remained unchanged, whereas modulation of the parent crystal structure changed when the sample was heat–treated above 1000 °C. This structural change to the unique modulated structure can be attributed to be the possible rearrangement of Al/Si distribution in the tetrahedral sites forming the framework.