Formation of six-coordinated silicon in calcium phosphosilicate xerogels assisted by polyols at low temperature and pressure

Abstract

Abstract Silicon is usually found to be four-coordinated when neighbored with oxygen. Six-coordinated silicon is only seen in samples at very specific composition or made at high temperature/pressure. In this study, we managed to synthesize calcium phosphosilicate xerogels containing six-coordinated silicon with the help of polyols by sol–gel method, without the need of treatment at high temperature or high pressure. Both phosphorus precursors and polyols were found to be essential for the formation of six-coordinated silicon species; in the absence of either species, only normal four-coordinated silicon was observed under otherwise identical conditions. Samples containing six-coordinated silicon sites were found to release silicon species faster than those without six-coordinated silicon sites upon dissolved in water, suggesting that six-coordinated silicon species have higher reactivity toward hydrolysis.