Stability of Zirconium-Substituted Face-Centered Cubic Yttrium Hydride

Area of Science:

• Materials Science
• Solid-State Chemistry
• Hydrogen Storage Materials

Background:

• Yttrium hydride (YH3) is a promising hydrogen storage material with a face-centered cubic (FCC) structure.
• Hydrogen atoms occupy tetrahedral (T) and octahedral (O) sites within the FCC lattice.
• Zirconium (Zr) substitution is explored to tune the properties of yttrium hydride.

Purpose of the Study:

• To investigate the stability and hydrogen site occupancy in zirconium-substituted yttrium hydride (Y1-xZrx hydride).
• To determine the influence of Zr content on hydrogen absorption/desorption behavior.
• To elucidate the preferential occupation of hydrogen sites based on Zr coordination.

Main Methods:

• Experimental investigation using Pressure-Composition (P-C) isotherms.
• Theoretical analysis using first-principles calculations.
• Evaluation of hydrogen content per metal (H/M) ratio and site occupancy.

Main Results:

• Zr substitution in YH3 resulted in a lower H/M ratio (2.2-2.3) than expected.
• Hydrogen primarily occupied O-sites during hydrogen desorption/absorption.
• Theoretical analysis showed that hydrogen atoms avoid O-sites when coordinated with two or more Zr atoms, with near-zero occupancy at >50% Zr content.

Conclusions:

• Zr substitution significantly reduces hydrogen occupancy at O-sites in FCC YH3.
• The distribution of hydrogen atoms is strongly influenced by the local coordination environment of Zr.
• Understanding these site occupancies is crucial for designing advanced metal hydride materials for hydrogen storage.