MDSC AND DSC STUDIES ON SOL-GEL LITHIUM TRIBORATE GLASS AND GLASS-CERAMICS - A COMPARISON

Glasses prepared following a sol-gel route must be thermally treated t o evacuate solvent and organic radicals. They often undergo phase tran sitions in the same temperature range where the weight tosses occur. W hen applied to these systems, conventional differential scanning calor imetry (DSC) may lead to deceiving interpretations. In this paper the transformations of a sol-gel lithium triborate glass, annealed up to 5 00 degrees C, have been investigated by Modulated DSC (MDSC). We show how the reversing heat flow signal obtained by temperature modulation may give valuable information. Upon annealing, the system undergoes ph ase separation and partial devitrification to give crystalline lithium diborate. A careful comparison with the misleading conclusions offere d by conventional DSC is performed. (C) 1997 Elsevier Science B.V.