The reported anomalous emission intensity of the 5D0 → 7F4 transition of Eu3+ in a molybdate double perovskite

Abstract

The assigned anomalous upconversion emission intensity of the 5D0 → 7F4 transition of Eu3+ in the double perovskite Sr2Ca(W1-xMox)O6 co-doped with Yb3+ is shown to be due to a transition metal impurity present in the MoO3 starting material. Relevant literature shows that the highest energy 5D0 → 7F4 transition is at a longer wavelength than 685 nm in molybdates. Cases of anomalous intensity of this transition are reviewed. Our 360 nm excited emission spectra of Sr2Ca0.88-Eu0.02Yb0.04Li0.06MoO6 show a very weak 5D0 → 7F4 transition, but on co-doping with Mn a structured band between 640 and 710 nm is observed due to Mn4+.