PREPARATION AND INFRARED STUDY OF MAGNESIUM BORATE GELS WITH A WIDE COMPOSITION RANGE

Gels in the system xMgO .(1-x)B2O3 (0.42 less than or equal to x less than or equal to 0.80) have been prepared by hydrolytic polycondensati on of boron-butoxide with magnesium methoxide in alcoholic medium. The gels were heated at 400 degrees C in order to obtain organic-free amo rphous materials. The infrared spectra of these gels reveal the progre ssive modification of the berate network with increasing magnesium per centage. The X-ray diffraction patterns of the gels show that calcinat ion at temperatures higher than 400 degrees C leads to crystallization of the amorphous network. For the very high magnesium content glass ( x = 0.80), evidence for magnesium carbonate formation is detected.