Structural and spectroscopic behaviour of Eu3+-doped SrGd2O4 modified by thermal treatments

Herein, SrGd2O4:Eu3+ phosphors were synthesized by homogeneous precipitation method followed by combustion process. With an increase in processing temperature from 800 to 1200 A degrees C, these phosphors showed a systematic change from a mixed low crystalline phase to a highly crystalline single phase. The samples, annealed at 1200 A degrees C, were crystallized into orthorhombic phase without any impurities. Microscopic studies revealed the irregular morphology of the obtained phosphor particles having sizes in the range of 0.5-5 mu m. UV-excited phosphors exhibited strong red emissions owing to the homogeneous occupation of Eu3+ ions in the host. With the enhancement in Eu3+ concentrations up to 4 mol%, the emission intensity was observed to increase systemically, and decreased above 4 mol% owing to the concentration quenching. The critical distance for the quenching mechanism was calculated to be 17.11 suggesting multipolar interactions between Eu3+ ions. The dominant red-to-orange intensity ratios (2.59) and Judd-Ofelt parameters of Eu3+ ions supported the strong covalent nature and site-occupation of higher asymmetry sites of Gd3+ ions. The red colour purity was increased with Eu3+ concentration and obtained to be 95 % for SrGd2O4:4 mol% Eu3+ sample. Efficient red emission with high colour purity and elevated chemical durability indicated the suitability of SrGd2O4:Eu3+ phosphor for display applications.