Relationship between Eu3+ substitution sites and photoluminescence properties of SrIn2O4:Eu3+ spinel phosphors

Abstract

Eu 3+-doped SrIn2O4 phosphors were synthesized by the solid solution method at 1400 ºC in air. The chemical composition of the phosphors was systematically changed to study the relation between the Eu 3+ substitution site and photoluminescence (PL) properties. Under excitation of the 7 F0→ 5 L6 transition of Eu 3+ at 393 nm, the SrIn2O4:Eu 3+ exhibited dominant red emission peaks at 611, 616 and 623 nm, which are attributed to the electric dipole transition 5 D0→ 7 F2 of Eu 3+. The results of X-ray diffraction analysis combined with PL spectroscopic analysis revealed that Eu 3+ ions occupied two different crystallographic In 3+ sites in the host SrIn2O4, while it was found to be impossible to substitute Sr 2+ with Eu 3+ prior to the Eu 3+ substitution at the In 3+ sites in the SrIn2O4. The intensity of the red emission peaks increased with the total amount of dopant Eu 3+ ion at the two In 3+ sites, and reached a maximum at 25 mol% Eu 3+-doping (SrIn2-xO4:xEu 3+ , x=0.25). Moreover, a small amount (<10 mol%) of Eu 3+ at the Sr 2+ site in the SrIn2-xO4:xEu 3+ was found to contribute to enhance the red emission peak intensity at 616 nm. As a result, the highest red emission intensity evaluated as the total emission peak intensities at the 611, 616 and 623 nm was achieved for Sr0.92In1.75O4:0.33Eu 3+ in which Eu 3+ ion concentrations at the In 3+ and Sr 2+ sites were simultaneously optimized as 25 and 8 mol%, respectively (Sr1-yIn2-xO4:(x+y)Eu 3+ , x=0.25, y=0.08). This red emission intensity was 2.2 times higher than that of the phosphor without contribution of the Eu 3+ at the Sr 2+ site (SrIn2-xO4:xEu 3+ , x=0.25). The critical energy transfer distance of Eu 3+ ion in the Sr0.92In1.75O4:0.33Eu 3+ phosphor was determined to be 0.817 nm, and the electric multipolar interaction was suggested as the dominant mechanism for concentration quenching of PL emission due to Eu 3+ ions in the Eu 3+-doped SrIn2O4 phosphors investigated in this study.

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Influence Ca-doped SrIn2O4 powders on photoluminescence property prepared one step by ultrasonic spray pyrolysis

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