Luminescence properties of PbWO4:Eu3+ nanocrystals synthesized by a hydrothermal method

PbWO4:Eu3+ nanocrystals were synthesized by the hydrothermal method at different temperatures. Their luminescence properties were studied systemically. The results indicate that the particle sizes of the nanocrystals increase with increasing hydrothermal temperature. Estimated according to Scherrer's equation, the crystallite sizes are in the range of 10-15 nm, 20-30 nm, and 35-40 nm at the hydrothermal temperatures of 120 degrees C, 150 degrees C, and 180 degrees C, respectively. Because of the slight aggregations of powders, nanocrystal sizes observed by TEM are larger than the crystallite sizes estimated by XRD patterns. The excitation spectrum shows four excitation bands. The excitation band with the maximum at 264 nm can be attributed to the charge-transfer band of W6+-O2- within the WO42- group and O-Eu CT band. The bands at 372 nm, 458 nm, and 536 nm can be assigned to the electronic transitions of Eu3+ ions. In the emission spectrum, the D-5(0)-> F-7(J) transitions (J=1, 2,3 and 4) can be observed clearly. But the band emissions caused by tungstate groups are not observed. The concentration of europium has an influence on the luminescence of samples. (C) 2013 Elsevier Ltd. All rights reserved.