DEHYDRATION PROCESS OF LITHIUM BORATES

Li(H2O)(4)B(OH)(4) . 2H(2)O, Li3B5O8(OH)(2), Li(H2O)B2O3(OH) and Li(H2 O)(3)B5O6(OH)(4) were synthesized and their dehydration were studied u sing various thermal analyses and also by examination of their crystal structure and especially the modification of Li+ coordination during dehydration. As expected, the adsorbed water leaves the structure belo w 100 degrees C; then the structural free water molecules and after th at the water molecules coordinated to Li escape. Finally, the OH group s leave the framework. The surrounding of the lithium atoms governs th e dehydration process; when its surrounding falls below four, the fram ework collapses and an amorphous phase is generally obtained. Therefor e, there are no relationships between the structure of the anhydrous b erates - LiBO2, LiB2O3.5 (or Li2B4O7), LiB5O8 and also LiB3O5 which ca n be obtained from mixture of two precursors - and the structure of th eir hydrated precursors.