Stabilization of high temperature tysonite type compounds in the Sr-Yb-F system-synthesis and Rietveld refinement

Several compositions of the type SrxYb1-xF3-x (x = 0.20, 0.25, 0.30. 0.33) were prepared by heating the well ground mixtures of appropriate amounts of SrF2 and YbF3 at 1100 degreesC. The substitution of Yb3+ in YbF3 bY Sr2+ f or x=0.25 and 0.3 leads to new single phasic fluorides with tysonite type s tructure, Quenching was shown to be essential to stabilize these phases, Th e XRD pattern of Sr0.25Yb0.75F2.75, i.e., SrYb3F11 was fitted on a hexagona l unit cell with space group P6(3)/mmc with a = 3.9606(4) and c 6.9731(5) A ngstrom. According to Rietveld refinements the as prepared SrYb3F11 crystal lizes in the disordered HT-form of the tysonite type structure, The magneti c measurements of Sr0.25Yb0.75F2.75 show paramagnetic behaviour with a magn etic moment of 4.6 mu (B) which corresponds to the f(13) configuration of Y b3+. (C) 2001 Elsevier Science Ltd. All rights reserved.