Structural understanding of the spectral characteristics of SnO2:Eu:Y2O3, using extended x-ray absorption fine structure

Abstract

SnO 2 : Eu is a well-known luminescent material, emitting red and orange lines. The intensity ratio of red to orange emission, being sensitive to the deviation of Eu3+ ions from symmetric location, finds wide application as sensor. The luminescence intensity of such lanthanide-doped sensors is generally optimized by high temperature annealing. However, for the present system (SnO2:Eu) it had been found that the red emission suddenly disappears while annealing beyond 900 °C, which can however be recovered by dispersing the system in a secondary host matrix of Y2O3. Understanding the mechanism of this recovery has important implication for designing of phosphor. In this work, we structurally explain this spectral evolution, by employing x-ray absorption fine structure technique. The initial disappearance of the red line is realized to be due to the formation of Eu2Sn2O7 and the recovery, to the intercalation of the Eu3+ ions from the SnO2 surface into Y2O3. Oxygen vacancy in Y2O3 creates the asymmetric environment required for red line emission. The design implications of these findings are discussed.