High-Pressure Synthesis of Novel Polyhydrides of Zr and Hf with a Th4H15-Type Structure

• Published in: Journal of physical chemistry. C 2019-12, Vol.123 (50), p.30059-30066
• Main Authors: Kuzovnikov, Mikhail A, Tkacz, Marek
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.9b07918

The reaction of ZrH2 and HfH2 with molecular hydrogen was studied by in situ X-ray diffraction in a diamond anvil cell at room temperature at high pressures of up to 39 GPa. The formation of novel zirconium and hafnium hydrides was observed at 8.2(5) and 12.4(5) GPa, respectively. These new hydrides had the cI16-type structure of a metal lattice, identical to that of Th4H15, and the compositions of new hydrides were estimated to be Zr4H15 and Hf4H15 on the basis of their lattice volumes. The decomposition of these hydrides back into ZrH2 and HfH2 during decompression was observed at 3.5(3) and 3(1) GPa, respectively. Electrical resistance measurements indicated that Hf4H15 is a superconductor with T c ≈ 4.5 K at 23 GPa.