Uniaxial Negative Thermal Expansion and Mechanical Properties of a Zinc-Formate Framework

• Published in: Materials Vol. 10; no. 2; p. 151
• Main Authors: Gao, Hongqiang, Wei, Wenjuan, Li, Yizhang, Wu, Rong, Feng, Guoqiang, Li, Wei
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 10.02.2017; MDPI
• Subjects: Anisotropy; Crystals; Elastic properties; Hardness; Mechanical properties; mechanical property; Metal formates; metal-formate framework; Modulus of elasticity; Nanoindentation; negative thermal expansion; Single crystals; Stiffness; Thermal expansion; Zinc; mechanical property; negative thermal expansion; metal-formate framework
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma10020151

The thermal expansion behavior of a metal-formate framework, Zn(HCOO)₂·2(H₂O) ( ), has been systematically studied via variable temperature single-crystal X-ray diffraction. Our results demonstrate that this formate exhibits significant negative thermal expansion (NTE, -26(2) MK ) along its -axis. Detailed structural analyses reveal that the large NTE response is attributed to the 'hinge-strut' like framework motion. In addition, the fundamental mechanical properties of framework have been explored via nanoindentation experiments. The measured elastic modulus and hardness properties on the (00-2)/(100)/(110) facets are 35.5/35.0/27.1 and 2.04/1.83/0.47 GPa, respectively. The stiffness and hardness anisotropy can be correlated well with the underlying framework structure, like its thermoelastic behavior.