Preparation, Structure, and Up-Conversion Luminescence of Yb3+/Er3+ Codoped SrIn2O4 Phosphors

SrIn2O4, which shows lower phonon energy than CaIn2O4, is not only a good photocatalyst but also can be an excellent up-conversion (UC) host to exhibits UC luminescence. In this work, Yb3+ and/or Er3+ doped SrIn2O4 phosphors were synthesized, and their UC luminescence properties were studied and compared with those in the CaIn2O4 host. The structure of SrIn2O4: 0.01Er(3+) and SrIn2O4: 0.1Yb(3+)/0.01Er(3+) samples were refined by the Rietveld method and found to that SrIn2O4: 0.1Yb(3+)/0.01Er(3+) showed increasing unit cell parameters and cell volume, indicating In3+ sites were substituted successfully by Yb3+ and/or Er3+ ions. From the UC luminescence spectra and diffuse reflection spectra, Er3+-doped SrIn2O4 showed very weak luminescence due to ground state absorption of Er3+; Yb3+/Er3+ codoped SrIn2O4 presented strong green (550nm) and red (663nm) UC emissions which were assigned to energy transfer from Yb3+ transition (F7/2F5/2)-F-2-F-2 to the Er3+ transition S-4(3/2) I-4(15/2) and F-4(9/2) I-4(15/2). Comparing with CaIn2O4, Yb3+/Er3+ codoped SrIn2O4 showed obvious advantages with higher UC luminescent intensity. The pumping powers study showed that UC emissions in Yb3+/Er3+ codoped SrIn2O4 were attributed to energy transfer of Yb3+Er3+ with a two-photon process. The possible UC luminescent mechanism of Yb3+/Er3+-doped SrIn2O4 was discussed.