Abstract:
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 nmfor Y3Al5O12:Ce3+ arising fromthe 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.
Description:
This research was jointly funded by the South African Research
Chairs Initiative of the Department of Science and Technology,
the National Research Foundation of South Africa and University
of the Free State Cluster Fund.
