Silicon esters are silicon compounds that contain an oxygen bridge from silicon to an organic group, for example, Si-OR.
The tetraalkyl orthosilicates ( also called orthosilicic acid esters) most commonly used as starting materials for sol-gel.
Polysilicic acidesters are condensation products obtained by incomplete hydrolysis or orthosilicic acid esters. They are also be used as starting materials for the sol-gel process.