Charge transfer bands of Mo-O and photoluminescence properties of micro-material Y2MoO6:Eu3+ red phosphor

Eu3+ activated micrometer Y2MoO6 phosphors with strong red emission bands, under a broad-band excitation wavelength range of 340-400 nm, have been prepared by solid-state reaction and sol-gel technique. The photoluminescence indicates that the materials exhibit a characteristic red emission peak of Eu3+ ions at 612 nm. Compared with the material obtained by sol-gel method, the Y2MoO6:Eu prepared using solid state method showed much stronger red emission under the n-UV excitation. The broad excitation bands are assigned to charge transfer (CT) bands originating from the ligands (O) to the central ions Mo6+. About 12 nm shift of excitation bands in Y2MoO6:Eu was found. With a decrease of the crystalline size, the excitation bands of O-Mo CT shift to the short wavelength. The origin of CT shift in macromaterial Y2MoO6:Eu was investigated quantitatively from the chemical bond viewpoint. All constituent chemical bonds in the crystal with or without oxygen vacancy were considered. The changes of average energy gap of the chemical bond Mo-O and the environmental factor (he) surrounding Mo6+ ions in the crystals were discussed quantitatively. Calculated results from two different methods analysis specifications showed that the origin of CT blue-shifts mainly come from the vacancies of O6 sites within the crystals.