Download all files (5.58 MB)

Collection

Citation

Description:

The high-pressure (HP)/high-temperature (HT) phase diagram of barium hydride (BaH2) was investigated using X-ray diffraction measurements and diamond-anvil cells to clarify the relationships between some phases, including the hydride-ion (H–) conductive HT phase that adopts the Ni2In-type structure. The results revealed that the HT phase and the HP phase were the same in the phase diagram and constitute an HP/HT phase. Furthermore, it was found that the Ni2In-type structure is stable over a wide range up to approximately 50 GPa and 500 ℃. The coexistence of two phases during the phase transition may be responsible for the previously reported anomalous pressure dependency of ionic conductivity in the HP phase. Additionally, the HP/HT phase diagram of strontium hydride (SrH2), which exhibits a similar HP structural sequence, was also investigated. It was found that the Ni2In-type structure of SrH2 is stable at pressures above 7 GPa within the temperature range of this work (~500 ℃). These wide stable HP/HT regions imply that the structural properties of hydride-ion conductive BaH2 and SrH2 can be investigated under the wide conditions in the future. Furthermore, the pressure dependence of the lattice parameters and volume was obtained, and the bulk moduli of BaH2 and SrH2 in the Ni2In-type structure are determined to be 31.5(15) GPa and 42.4(7) GPa, respectively. The pressure dependence of the crystallographic parameters obtained in this study will be useful for understanding the origin of the properties from the crystallographic viewpoint in future work.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: barium hydride, strontium hydride, hydride-ion conduction, high-pressure and high-temperature, phase diagram

Date published: 2026-12-31

Publisher: Informa UK Limited

Journal:

• Science and Technology of Advanced Materials (ISSN: 14686996) vol. 27 issue. 1 2691690

Funding:

• MEXT/JSPS KAKENHI 24K01445 and 25K01508
• Tokodai Institute for Elemental Strategy, MEXT Element Strategy Initiative to Form Core Research Center, Japan JPMXP0112101001
• MEXT/JSPS KAKENHI JP18K05284
• MEXT/JSPS KAKENHI JP21H00030
• MEXT/JSPS KAKENHI 24K01427

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1080/14686996.2026.2691690

Related item:

Other identifier(s):

Contact agent:

Updated at: 2026-07-10 08:46:57 +0900

Published on MDR: 2026-07-10 10:24:21 +0900