Si2Al2O7

Si2Al2O7 is an oxide compound consisting of silicon, aluminum, and oxygen in a 1:1 Si:Al ratio. The formula can be written as Al2Si2O7 to emphasize its aluminosilicate composition. It is part of the broader aluminosilicate family, in which silicon and aluminum occupy tetrahedral coordination sites linked by shared oxygen atoms.

Structure and chemistry: In aluminosilicate frameworks, silicon and aluminum are four-coordinated to oxygens (forming SiO4 and AlO4 tetrahedra) that share corners to create a three‑dimensional network. The presence of Al3+ in the tetrahedral framework introduces a framework charge that must be balanced by the overall composition; for Al2Si2O7, the charges balance with seven oxide anions per formula unit. The arrangement can exhibit various crystallographic polymorphs or degrees of disorder depending on synthesis conditions.

Occurrence and synthesis: Si2Al2O7 is more commonly encountered as a synthetic or metastable phase within the SiO2–Al2O3 system than as a widely recognized natural mineral. It can be produced by solid-state reaction of silicon dioxide and aluminum oxide at elevated temperatures, or by sol–gel and hydrothermal methods that yield crystalline aluminosilicate phases with a 1:1 Si:Al ratio.

Properties and applications: The properties of Si2Al2O7 depend on its precise crystal structure but are characteristic of aluminosilicate-like materials, including high thermal stability and chemical durability. Such materials are of interest in ceramic and glass-ceramic applications and serve as model compositions for studying the behavior of 1:1 aluminosilicate frameworks and their phase relations in the SiO2–Al2O3 system.