Structural and Mossbauer spectroscopic study of hexagonal Laves-phase Zr(FexCr1-x)2 alloys and their hydrides

Hexagonal (C14) Laves-phase Zr(FexCr1-x)(2) alloys with x=0.3, 0.4, 0.5, 0.6 and 0.7 have been prepared by are melting and the corresponding hydrides have been formed by hydrogen uptake at 1 arm pressure. X-ray diffractograms have been measured and analyzed with the Rietveld method. Fe-57 Mossbauer spectra, measured at room temperature, could be fitted with two doublets with 3:1 area ratio, corresponding to the two Fe sites in the C14 structure. The quadrupole splitting (Delta) and isomer shift (delta) dependences on x are discussed in terms of volume and charge effects. The hydrides showed volume expansions of up to 22% without any crystal structure change. Both Mossbauer hyperfine parameters Delta and delta increased markedly in the hydrides as compared to the alloys. Tetrahedral hole radii have been calculated from measured crystalline parameters and their relationship to hydrogen site preferences is discussed. (C) 1999 Elsevier Science S.A. All rights reserved.