Local structural analyses on molten terbium fluoride in lithium fluoride and lithium-calcium fluoride mixtures

X-ray absorption fine structure (XAFS) measurements on terbium fluoride in molten lithium fluoride and in molten lithium-calcium fluoride mixtures, (e.g. 0.20TbF(3)-0.80LiF, 0.20TbF(3)-0.62LiF-0.18CaF(2), 0.20TbF(3)-0.48LiF-0.32CaF(2), 0.50TbF(3)-0.50LiF, and 0.50TbF(3)-0.38LiF-0.12CaF(2)), have been carried out. In the solid state, coordination number of terbium (I 11) and inter ionic distances between terbium and fluorine in the first neighbor (r(i)) are nearly constant in all mixtures. In 0.20TbF(3)-0.80LiF, 0.20TbF(3)-0.62LiF-0.18CaF(2) and 0.50TbF(3)-0.50LiF mixtures, N-i's decrease from ca. 8 to 6 and r(i)'s also decrease from ca. 2.29 to 2.26 angstrom on melting. On the other hands, in molten 0.20TbF(3)-0.48LiF-0.32CaF(2) and 0.50TbF(3)-0.38LiF-0.12CaF(2) mixtures, N-i's are slightly larger than 6 and r(i)'s do not change. These facts correspond to the amount of F- supplied by solvent melts, i.e. the effect of CaF2 becomes predominant at bCaF(2) >0.32 in ternary 0.20TbF(3)-aLiF-bCaF(2) mixtures and at bCaF(2) > 0.12 in ternary 0.50TbF(3)-aLiF-bCaF(2) mixtures. (C) 2010 Elsevier B.V. All rights reserved.