Effect of Ga3+ and Gd3+ ions substitution on the structural and optical properties of Ce3+‐doped yttrium aluminium garnet phosphor nanopowders

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.