Investigation on the Luminescence Improvement of Nanosized La2O3/Eu3+ Phosphor under Charge-Transfer Excitation

When the size of La2O3/Eu3+ phosphor decreases to the nanoscale, the rigidity of the lattice environment is decreased, causing the enlargement of the charge-transfer state (CTS) coordinate offset for the optical centers in La2O3/Eu3+ nanophosphor. The enlargement of the CTS coordinate offset results in the decrease of the CTS feeding probability to the D-S states of Eu3+ ions in the optical centers. In addition, the energy transfer.to the quenching centers in the surface leads to the decrease of the D-S emission efficiency of the excited Eu3+ ions. In view of these two quenching mechanisms of the optical centers, proper surface coating is adopted to improve the luminescence efficiency for La2O3/Eu3+ nanophosphor under CT excitation. The changes in the related parameters of La2O3/Eu3+ nanophosphor in the surface coating and the subsequent annealing process have been experimentally determined and objectively analyzed. By surface coating, the luminescence efficiency of La2O3/Eu3+ nanophosphor has been significantly improved.