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Giant Negative Thermal Expansion in Bonded MnCoGe-Based Compounds with Ni2In-Type Hexagonal Structure



Ying-Ying Zhao, Feng-Xia Hu, Li-Fu Bao, Jing Wang, Hui Wu, Qingzhen Huang, Rong-Rong Wu, Yao Liu, Fei-Ran Shen, Hao Kuang, Ming Zhang, Wen-Liang Zuo, Xin-Qi Zheng, Ji-Rong Sun, Bao-Gen Shen


MnCoGe-based compounds undergo a large negative thermal expansion (NTE) during the martensitic structural transition from Ni2In-type hexagonal to TiNiSi-type orthorhombic structure. High resolution neutron diffraction experiments revealed that the expansion of unit cell volume can be as large as Delt}V/V3.9%. The optimized compositions with concurrent magnetic and structural transitions have been studied for magnetocaloric effect. However, these materials have not been considered as NTE materials for practical applications up to now. The MnCoGe-based compounds are quite brittle and the as-prepared samples would naturally collapse the powders. Through introducing a few percents (3-4%) of epoxy to cohere the powders, controllable NTE (not only the linear NTE coefficient but also the operation-temperature window) has been achieved. For example, the linear NTE coefficient as high as 51.5x10-6K-1 with an operating temperature window as wide as 210K from 120 to 330K have been observed in a bonded MnCo0.98Cr^d0.02Ge compound. Such an excellent performance exceeds that of most other materials reported previously, suggesting it can potentially be used as good NTE material, particularly for compensating the materials with large positive thermal expansions.
Journal of American Chemical Society


negative thermal expansion, neutron diffraction, magnetic structure


Zhao, Y. , Hu, F. , Bao, L. , Wang, J. , Wu, H. , Huang, Q. , Wu, R. , Liu, Y. , Shen, F. , Kuang, H. , Zhang, M. , Zuo, W. , Zheng, X. , Sun, J. and Shen, B. (2015), Giant Negative Thermal Expansion in Bonded MnCoGe-Based Compounds with Ni<sub>2</sub>In-Type Hexagonal Structure, Journal of American Chemical Society, [online], (Accessed April 22, 2024)
Created February 10, 2015, Updated October 12, 2021