5 7Fe Mössbauer effect in ThFe5 hydride

Abstract

The hydrogen absorption in the CaCu₅‐type compound ThFe₅ was studied by x‐ray diffraction, magnetic measurements, and ⁵⁷Fe Mössbauer spectroscopy. Hydrogen absorption leads to a 6% increase of the unit cell volume without change in crystal structure. There is only a slight change in magnetic properties. The ⁵⁷Fe Mössbauer spectra of the ternary hydride are characterized by relatively sharp lines, an increase in hyperfine field, and an increase in isomer shift relative to the uncharged compound. The increase in ⁵⁷Fe isomer shift invariably observed after charging of Fe compounds with hydrogen is explained in terms of the Miedema–van der Woude model. The relatively low tendency of the hydride of ThFe₅ to decompose (disproportionate) as compared to some other Th‐Fe hydrides is explained on the basis of a kinetic approach.