Processing and structural characteristics of encapsulated ZnO in porous polysiloxane-derived ceramics

Abstract

A facile processing strategy based on a simple pressing and heat-treatment at 800°C in air or argon was successfully demonstrated for fabricating encapsulated ZnO in porous polysiloxane-derived ceramic matrix. The composite samples contain ZnO crystallites with wurtzite structure embedded in amorphous SiO 2 or SiOC matrix and have 5158% porosity depending on the starting polysiloxane content and heat-treatment atmosphere. For the samples heat-treated in air, the one with more ZnO content in the batch composition showed higher green-emission intensity as well as lower excitonic-emission intensity in photoluminescence (PL) spectrum compared to the one with less ZnO content. The result can be understood in terms of the amount of defects such as oxygen vacancies in the ZnO crystallites: the former has higher defect density than the latter. Raman spectra for the two samples support the interpretation. The samples heat-treated in argon exhibit weaker PL strength compared to the air-treated ones in the whole photon-energy range, attributable to the secondary phase (ZnSiO 3 ) formation.