Investigation on photoluminescence, electrical and positron lifetime of Eu3+ activated Gd2O3 phosphors

In the present study, red emitting Gd2O3:Eu3+ phosphors are prepared by citrate-based sol-gel process and the as-prepared samples are annealed at various annealing temperatures. The photoluminescence properties of Gd2O3:Eu3+ is explained from the excitation and emission spectra. The excitation spectra include peaks corresponding to charge transfer and 4f-4f transitions of Eu3+ and Gd3+. The phosphors exhibit a weak energy transfer process from Gd3+ to Eu3+. Under the excitation of 254 nm, a sharp red emission peak is observed at 611 nm and the emission intensity increases with the annealing temperature. The presence of defects in the phosphor is investigated by positron annihilation lifetime and Doppler broadening spectroscopy. The relation between visible emission and lattice defects of the phosphors is presented. The electrical and dielectric properties of the phosphor are also discussed in detail. Such red emitting phosphors pave the way towards the fabrication of light emitting diodes (LEDs).