SYNTHESIS OF LITHIUM BORATES (B LI-GREATER-THAN-OR-EQUAL-TO-3) AS LIB3O5 BY DEHYDRATION OF HYDRATED PRECURSORS/

LiB3O5 has been synthesized by dehydration of LiB2O3(OH). H2O and LiB5 O6(OH)(4) . 3H(2)O stoichiometric mixtures. The dehydration of the hyd rated pentaborate, LiB5O6(OH)(4) .3H2O, yields different results accor ding to the heating rate. The X-ray powder diffraction as a function o f temperature, at 6 degrees C per hour, has allowed us to observe the anhydrous pentaborate, LiB5O8, and to give, for the first time, its po wder diagram. This compound decomposes rapidly to give the tetraborate , Li2B8O13. Li2B8O13 crystallographic characteristics have been establ ished from single crystal studies: monoclinic system with a=17.764(5) Angstrom, b=7.789(2) Angstrom, c=9.667(4) Angstrom and beta=100.95(2)d egrees. This compound also decomposes to give LiB3O5, a more complete powder diagram of which is given.