Investigation on luminescence properties of Dy3+-, Eu3+-doped, and Eu3+/Dy3+-codoped SrGd2O4 phosphors

Dy3+-, Eu3+-doped, and Eu3+/Dy3+-codoped SrGd2O4 scintillating phosphors were successfully synthesized by solid-state reaction. The phases of the obtained phosphors were analyzed by X-ray diffraction (XRD) and photoluminescent properties including excitation, emission and decay behavior of Dy3+ and Eu3+ activators were systematically investigated. Our results revealed that the optimal content of Dy2O3 and Eu2O3in SrGd2O4 phosphors is 2 mol%, and 20-25 mol%, respectively. In comparison with the optimal Eu3+-doped SrGd2O4 phosphor, the optimal Eu3+/Dy3+-codoped SrGd2O4 one shows a one-time increase in the intensity of X-ray excited luminescence (XEL) from 613 nm emission of Eu3+. This increase was ascribed to the efficient energy transfer from Dy3+ to Eu3+ ions. The mechanism of energy transfer was discussed by the Dexter's theory in detail.