Rhombohedral Fe17Pr2Hx compounds having the Zn17Th2 structure were prepared with x-values ranging from 0 to 5. Their lattice parameters and Curie temperatures were deduced from powder X-ray diffraction and thermomagnetic measurements, and their Mössbauer spectra were measured at temperatures of between 4.2 and 295K. The Mössbauer spectra for x = 0, 1 and 2, at temperatures of 4.2 to 295K, and those of Fe17Pr2H3 above 90K, were analyzed in terms of a 7-sextet model. The Mössbauer spectra of Fe17Pr2H3 below 90K, of Fe17Pr2H4 between 4.2 and 295K, and of Fe17Pr2H5 above 155K, were analyzed in terms of a 4-sextet model. The Mössbauer spectra of Fe17Pr2H5 indicated that, above 155K, the two H atoms which occupied one third of the tetrahedral 18g sites were rapidly jumping, at a Mössbauer time-scale of 100ns, between the 6 available 18g positions. This jumping slowed down, or ceased, below 155K. The compositional dependence of the hyperfine parameters of the Fe17Pr2Hx compounds indicated an initial filling of the interstitial 9e sites by the first three H atoms, followed by subsequent filling of the interstitial 18g sites by the last two H atoms.

Hydrogen Dynamics in the Hydrides of Pr2Fel7 as Revealed by Mössbauer Spectroscopy. D.Hautot, G.J.Long, F.Grandjean, O.Isnard, S.Miraglia: Journal of Applied Physics, 1999, 86[4], 2200-7