Thermally induced cation ordering in ZnAl2O4:Mg2+, Fe3+ for sensing thermal history through photoluminescence

Abstract

Applicability of spinel compounds is mainly governed by cation distribution in them. In the presented study, thermally induced cation ordering is found to influence the emission color of Mg2+, Fe3+ co-doped ZnAl2O4 spinel. Cation distribution is monitored through Mg K-edge, Fe L-2,L-3-Ledge, O K-edge X-ray absorption near edge structure spectroscopy and X-ray diffraction analysis using synchrotron radiation. Thermal treatment provided sufficient energy to Zn2+, Mg2+, Al3+ and Fe3+ cations to redistribute themselves on tetrahedral and octahedral sites, and reduce the octahedral distortion, thereby gaining stability. Reduced inversion accompanied by decrease in oxygen vacancies, while increase in tetrahedral and octahedral site vacancies contributed toward more intense blue emission band and quenched yellow band, changing the emission color from bluish-white to blue. Correlation derived between cation ordering and luminescence upon thermal treatment predict Mg2+, Fe3+ co-doped ZnAl2O4 nanophosphors to be useful in thermal sensing applications.