Luminescent properties of rare earth (Er, Yb) doped yttrium aluminium garnet thin films and bulk samples synthesised by an aqueous sol–gel technique

Yttrium aluminium garnet (YAG) powders and thin films deposited on silicon substrates were prepared by an aqueous sol–gel route using metal nitrates. The sol–gel process resulted in an amorphous gel, and the thermal decomposition and successive crystallization were characterized by thermal analysis and X-ray diffraction. Powders were prepared by heat treatment of the amorphous gel, while crack-free thin films of densely packed nano-crystalline particles were obtained on silicon substrates by dip-coating technique. Photoluminescence (PL) properties as well as up-conversion (anti-stoke emission) of Er, Yb co-doped YAG phosphors were investigated. Green (555 nm) and red (650 nm) photoluminescence up-conversion emissions arising due to 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions, respectively for Er3+ ion were observed. Photoluminescence and radiative life-times of the exited states of Er3+ in the visible and near IR ranges are also reported.