Effect of sintering temperature on the structural and luminescence properties of Er doped PbWO 4 microcrystals

Erbium-doped lead tungstate (PbWO4) microcrystals with different doping concentrations have been synthesized using an aqueous precipitation method under the assistance of cetyltrimethyl ammonium bromide (CTAB). The results characterized by X-ray diffraction and scanning electron microscope show that the tetragonal stolzite microcrystals with a spindle-like shape form flower-like and fork-like microstructures. The band gap was widened due to the structural relaxation after sintering at 873 K. The analysis of Fourier transform infrared transmittance spectra and photoluminescence spectra shows that the excited states of Er3+ ions could be de-excited by the quenching effect from OH and CH2 groups and energy transfer to the defects in the as-obtained samples. The Er3+ ions in the PbWO4 host could be activated via releasing the OH group and the decomposition of the CTAB on the surface of the microcrystal. When the sintered samples were placed for 5 months the green emission peaks of the active Er3+ ions at 523 nm, 529 nm, 544 nm and 551 nm are merged as two peaks at 532 nm and 554 nm because of line broadening from the further relaxation of the structure and the change of the crystal field in the microcrystals.