Chem. J. Chinese Universities ›› 2022, Vol. 43 ›› Issue (6): 20220124.doi: 10.7503/cjcu20220124

• Physical Chemistry • Previous Articles     Next Articles

Uniaxial Negative Thermal Expansion and Mechanism in Zn(NCN)

SHI Naike1, ZHANG Ya1, SANSON Andrea2, WANG Lei3, CHEN Jun1()   

  1. 1.Beijing Advanced Innovation Center for Materials Genome Engineering,Department of Physical Chemistry,University of Science and Technology Beijing,Beijing 100083,China
    2.Department of Physics and Astronomy,University of Padova,Padova I? 35131,Italy
    3.Department of Physics,University of Science and Technology Beijing,Beijing 100083,China
  • Received:2022-03-01 Online:2022-06-10 Published:2022-04-11
  • Contact: CHEN Jun E-mail:junchen@ustb.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(22101020);the Fundamental Research Funds for the Central Universities, China(20-041A2)

Abstract:

As an abnormal physical phenomenon, negative thermal expansion(NTE) has been observed in some materials like alloys and framework structure materials. However, the types of NTE materials are still limited. In this study, a uniaxial NTE material Zn(NCN) was synthesized. The coefficient of thermal expansion of the c-axis is -3.35×10?6 K?1 of 100—475 K, while the a and b axes show low thermal expansion. The volume of Zn(NCN) has a low coefficient of thermal expansion(αvca. 6.13×10?6 K?1, 100—475 K). The NTE mechanism was revealed by joined methods of synchrotron X-ray diffraction, extended X-ray absorption fine structure spectroscopy, and Raman spectra. It is found that the Zn—N exhibits obvious transverse vibration. Some low frequency vibration modes show negative Grüneisen parameter. The direct experimental evidence reveals that the transverse vibration of N=C=N linkage and coupling rotation and twist of quasi rigid ZnN4 tetrahedra result in the NTE in the c-axis.

Key words: Negative thermal expansion, Framework structure, Crystal structure, Zinc cyanamide, Transverse vibration

CLC Number: 

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