Characterization, photoluminescence, thermally stimulated luminescence and electron spin resonance studies of Eu3+ doped LaAlO3 phosphor

Europium-doped lanthanum aluminate (LaAlO3) powder was prepared by using a combustion method. The crystallization, surface morphology, specific surface area and luminescence properties of the samples have been investigated. Photoluminescence studies of Eu doped LaAlO3 showed orange-reddish emission due to Eu3+ ions. LaAlO3:Eu3+ exhibits one thermally stimulated luminescence (TSL) peak around 400 °C. Room temperature electron spin resonance spectrum of irradiated phosphor appears to be a superposition of two centres. One of them (centre I) with principal g-value 2.017 is identified as an O− centre while centre II with an isotropic g-value 2.011 is assigned to an F+ centre (singly ionized oxygen vacancy). An additional defect centre observed during thermal annealing around 300 °C grows with the annealing temperature. This centre (assigned to F+ centre) originates from an F-centre (oxygen vacancy with two electrons) and the F-centre along with the associated F+ centre appear to correlate with the observed TSL peak in LaAlO3:Eu3+ phosphor. The activation energy for this peak has been determined to be 1.54 eV from TSL data.

Thermal annealing behaviour of centre III in LaAlO3:Eu phosphor.Figure optionsDownload as PowerPoint slide