Negative thermal expansion and phase transition of low-temperature Mg2NiH4

• DOI: 10.1016/j.jma.2022.09.012
• Publication Date: 2022-10-12T15:09:45Z
• Authors: Qun Luo; Qi Cai; Qinfen Gu; Yu Shi; Bin Liu; Xuan Quy Tran; Syo Matsumura; Tong-Yi Zhang; Kazuhiro Nogita; Tao Lyu; Qian Li; Fusheng Pan
• Keywords: Negative Thermal Expansion; Volume fraction; Powder Diffraction; Atmospheric temperature range

The negative thermal expansion (NTE) phenomenon is of great significance in fabricating zero (ZTE) materials to avoid shock during heating and cooling. NTE observed limited groups materials, e.g., metal cyanides, oxometallates, metal-organic frameworks, but has not been reported the family hydrides. Herein, a colossal continuous firstly developed low-temperature phases LT1- LT2-Mg2NiH4 between 488 K 733 from in-situ transmission electron microscope (TEM) video, with volume contraction reaching 18.7% 11.3%, respectively. mechanisms for LT1 LT2 are elucidated viewpoints phase transformation, magnetic transition, dehydrogenation, which different common containing flexible polyhedra units structure. linear shrinkage temperature 488–553 corresponds transition LT2→HT coefficient –799.7 × 10–6 K–1 revealed by synchrotron powder X-ray diffraction. sudden 493 may be caused rapid dehydrogenation Mg2Ni. single composite material structures would significant preparing tuning fraction phases.