Effect of Oxygen Vacancies on the Reduction of Eu in MgCa(PO) in Air Atmosphere.

The paper reported the synthesis of mixed-valence Eu-doped MgCa(PO) by solid-state reaction in the air atmosphere. The luminescence measurements indicated that the obtained phosphors exhibit a broad bluish-green fluorescence of Eu and a sharp orange-red emission of Eu excited by 395 nm. The abnormal reduction mechanism could be explained by a charge compensation model. A tunable luminescence was realized based on the reduction of Eu to Eu changed along with increasing the sintering time. The reduction of Eu to Eu in MgCa(PO) host was effected by the oxygen vacancy defects when the samples sintered in different atmosphere and sintered for different lengths of time, and the oxygen vacancies which act as the electron traps were investigated with thermoluminescence. All of the results almost indicated the oxygen vacancy could weaken the reduction of Eu to Eu. Our investigation of MgCa(PO):Eu could provide a practical basis and theoretical basis to study the effect of oxygen vacancy on the emission of Eu ions.