X-ray diffraction investigation of the hexagonal-fcc structural transition in yttrium trihydride under hydrostatic pressure

Pressure induced structural transition of yttrium hydride has been investigated using synchrotron radiation X-ray diffraction measurement up to 24 GPa at room temperature. A reversible hexagonal-fcc transition with a wide intermediate region from I I to 20 GPa is confirmed, which is consistent with previously reported X-ray results. The diffraction patterns measured for the intermediate state are not interpreted in terms of a hexagonal-fcc coexisting state or as rare-earth structures with various metal-layer stacking sequences. The equation of state determined for the hexagonal-YH3 provides a bulk modulus B-0 of 71.9 GPa, which is nearly half of the previously reported value, but is within the range of values reported for other rare-earth metal trihydrides with hexagonal structures. (c) 2006 Elsevier Ltd. All rights reserved.