Sol–gel synthesis and crystallization of aluminum borosilicate

The Al2O3–B2O3–SiO2 system is explored; in the composition Al16B6Si2O37, 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, Al4B2O9 and B-mullite (Al18B4O33) in addition to some amorphous compositions of the aluminum borosilicate system rather than a pure crystalline Al16B6Si2O37 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.