Intrinsic [VO4]3− emission of cesium vanadate Cs5V3O10
Polycrystalline Cs5V3O10 micro-particles were synthesized by a solid-state reaction. The vanadate shows intrinsic self-activated luminescence of a single broad band with a peak at 520 nm, extending from about 400 nm to 720 nm. This asymmetric band is composed of two bands due to the electronic transitions from the 3T1 and 3T2 excited states to the 1A1 ground state in [VO4]3− centers. The same emission band was obtained for micro- and nanoparticles. It is suggested that the broadening of the emission band arises from single [VO4]3− molecules. The emission and decay curve profiles indicate that the emission is not due to different kinds of [VO4]3− centers but only one kind of [VO4]3− center. When the temperature is increased from 10 K to 450 K, the emission intensity increases below 150 K and decreases above 150 K, and an unusual blue shift is observed. The observed temperature dependence can be understood by the relaxation processes of the emitting 3T1 and 3T2 states including the thermal feeding by the lower-energy 3T1 state to the higher-energy 3T2 state.