Hydrothermal homogeneous urea precipitation of hexagonal YBO3:Eu3+ nanocrystals with improved luminescent properties

Well-crystallized YBO3:Eu3+ nanocrystals were prepared by a mild hydrothermal method in the presence of urea, and a pure hexagonal phase could be obtained at a low temperature of 200degreesC only. The photoluminescence spectra showed a remarkable improvement on the chromaticity as well as the luminescent intensity, compared with the samples synthesized by solid-state reaction (SR). The effects of the synthesis temperature, urea concentration, and the doping concentration of Eu3+ on the crystallization and luminescent properties were investigated. The results showed that both high temperature and low urea concentration were favorable to the formation of YBO3:Eu3+, and the ratio of red emission (D-5(0) --> F-7(2)) to orange emission (D-5(0) --> F-7(1)) increased with decreasing the synthesis temperature and the urea concentration. Furthermore, the samples exhibited a higher quenching concentration of Eu3+ in comparison with those prepared by the SR, which was beneficial to further enhancing the luminescent intensity. These synthesis-dependent phenomena were analyzed, and possible explanations were proposed. (C) 2003 Elsevier Inc. All rights reserved.