Sol–gel synthesis and crystallization of aluminum borosilicate

The Al 2O 3–B 2O 3–SiO 2 system is explored; in the composition Al 16B 6Si 2O 37, for the effect of the preparation conditions on the properties of the final product. The sol–gel method was tried to prepare this composition both in an aqueous and non aqueous media. The crystalline phases developed were found to be mullite, Al 4B 2O 9 and B-mullite (Al 18B 4O 33) in addition to some amorphous compositions of the aluminum borosilicate system rather than a pure crystalline Al 16B 6Si 2O 37 phase. XRD and FT–IR showed that the gel prepared in non-aqueous medium could be thermally treated giving some crystalline species at lower temperatures than the gel formed in aqueous medium. In contrast to this result, DTA of the former product show an exothermic change at higher temperature than that of the later. This change could be attributed probably to an oxidation rather than to crystallization.