SOL-GEL SYNTHESIS OF ZINC ORTHOSILICATE

A two-step sol-gel process between a nucleophilic addition on zinc by the Si-OH group was explored to prepare Zn2SiO4 powders from organometallic compounds. Hydrolysis of tetraethyl orthosilicate under less-than-or-equal-to3N HNO3 followed by reaction with diethylzinc and then condensation under 0.1 to approximately 15M NH4OH resulted in the formation of amorphous Zn2SiO4 particles approximately 10-20 nm in size. Infrared and Raman spectroscopic results suggest that this Zn2SiO4 consists mainly of a Si-O-Zn network which remained amorphous to 600-degrees-C. Heating (10-degrees-C/min) above approximately 700 and 900-degrees-C caused the formation of beta- and alpha-Zn2SiO4 powders, respectively, which appeared to coalesce but not sinter. A high concentration of NH4OH is preferred for the synthesis of a high-density gel which transforms at lower temperatures to crystalline polymorphs.