Thermal expansion anisotropy of β-TlInS₂ crystals in the course of phase transitions

ABSTRACT

Basing on the thermal expansion studies performed for β-TlInS₂ crystals in the course of their phase transitions, we have found that the crystals aged for one year are composed from at least two polytypes, which undergo phase transitions at different temperatures. The detailed analysis of anisotropy of the thermal expansion demonstrates that all of the diagonal components of the thermal expansion tensor associated with the eigensystem have almost the same modules but differ by their signs. This leads to appearance of an elliptical conical surface of zero thermal expansion. The orientation of this surface does not depend on the temperature in the temperature interval under study. We have also found that the thermal expansion coefficients along the crystallographic a and b axes are close to zero.

KEYWORDS:

• Ferroics
• thermal expansion
• polytypes
• anisotropy
• beta-thalium-indium disulphide

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Ministry of Education and Science of Ukraine [project # 0117U000802].