title: Effect of Ga3+and Gd3+ions substitution on the structural and optical properties of Ce3+-doped yttrium aluminium garnet phosphor nanopowders.
abstract: The structural and optical properties of commercially obtained Y3Al5O12:Ce3+phosphor were investigated by replacing Al3+with Ga3+and Y3+with Gd3+in the Y3Al5O12:Ce3+structure to form Y3(Al,Ga)5O12:Ce3+and (Y,Gd)3Al5O12:Ce3+. X-Ray diffraction (XRD) results showed slight 2-theta peak shifts to lower angles when Ga3+was used and to higher angles when Gd3+was used, with respect to peaks from Y3Al5O12:Ce3+and JCPDS card no. 73-1370. This could be attributed to induced crystal-field effects due to the different ionic sizes of Ga3+and Gd3+compared with Al3+and Y3+. The photoluminescence (PL) spectra showed broad excitation from 350 to 550 nm with a maximum at 472 nm, and broad emission bands from 500 to 650 nm, centred at 578 nm for Y3Al5O12:Ce3+arising from the 5d → 4f transition of Ce3+. PL revealed a blue shift for Ga3+substitution and a red shift for Gd3+substitution. UV-Vis showed two absorption peaks at 357 and 457 nm for Y3Al5O12:Ce3+, with peaks shifting to 432 nm for Ga3+and 460 nm for Gd3+substitutions. Changes in the trap levels or in the depth and number of traps due to Ce3+were analysed using thermoluminescence (TL) spectroscopy. This revealed the existence of shallow and deep traps. It was observed that Ga3+substitution contributes to the shallowest traps at 74 °C and fewer deep traps at 163 °C, followed by Gd3+with shallow traps at 87 °C and deep traps at 146 °C. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Department of Physics, University of the Free State, Phuthaditjhaba, South Africa. alihwako@gmail.com.
authors.forename: A H
authors.initials: AH
authors.lastname: Wako
authors.affiliation: Department of Physics, University of the Free State, Phuthaditjhaba, South Africa.
authors.forename: F B
authors.initials: FB
authors.lastname: Dejene
authors.affiliation: Department of Physics, University of the Free State, Bloemfontein, South Africa.
authors.forename: H C
authors.initials: HC
authors.lastname: Swart
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D002563:Cerium / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D005682:Gadolinium / Q000737:chemistry*; D005708:Gallium / Q000737:chemistry*; D007477:Ions; D053758:Nanoparticles / Q000737:chemistry*; D055095:Optics and Photonics; D014961:X-Ray Diffraction; D015019:Yttrium / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D007477:Ions; C503779:yttrium-aluminum-garnet; D002563:Cerium; D015019:Yttrium; D005682:Gadolinium; D005708:Gallium; D000535:Aluminum
keywords: (Y,Gd)3Al5O12:Ce3+ substitution; Y3(Al,Ga)5O12:Ce3+; thermoluminescence; trap depths