A LOCAL ORDER STUDY OF MOLTEN LINBO3 BY NEUTRON-DIFFRACTION

The total structure factor S(Q) and the total pair correlation function G(r) of liquid LiNbO3 have been investigated by neutron diffraction. The temperature dependence of the scattered intensity has been measured in the range of momentum transfer 0.3 angstrom-1 < Q < 16.2 angstrom-1 and the range of temperature 1623 K > T > 1490 K including an undercooling domain. A large variation of S(Q) with temperature was never observed. From an analysis of G(r) made with reference to the crystalline LiNbO3 structure, it was possible to confirm a local ordering similar to the crystalline one. The assumption of a change in the Nb coordination in the liquid near solidification is unfounded. The Nb atom remains octahedrally coordinated up to one hundred degrees above the melting point. The values of the first-neighbour distances r1Nb-O, r1O-O and r1Li-O and the coordination numbers nLi-O and nO-O can be explained by the presence of NbO6 octahedra bonded together by Li atoms in the melt.