Microwave-modified sol-gel process of NaY(WO4)(2): Ho3+/Yb3+ phosphors and the upconversion of their photoluminescence properties

摘要

NaY1-x(WO4)(2):Ho3+/Yb3+ phosphors with doping concentrations of Ho3+ and Yb3+ (x=Ho3+ + Yb3+, Ho3+ =0.05, 0.1, 0.2 and Yb3+ =0.2, 0.45) were successfully synthesized by the microwave-modified sol-gel method, and the upconversion of their photoluminescence properties was investigated. Well-crystallized particles showed a fine and homogeneous morphology with particle sizes of 2-5 mu m. Under excitation at 980 nm, the UC intensities of NaY0.7(WO4)(2):Ho0.1Yb0.2 and NaY0.5(WO4)(2) Ho0.05Yb0.45 particles exhibited yellow emissions based on a strong 550-nm emission band in the green region and a strong 655-nm emission band in the red region, which were assigned to the S-4(2)/F-5(4) -> I-5(8) and F-5(5) -> I-5(8) transitions, respectively. The Raman spectra of the doped particles indicated the presence of strong disordered peaks at higher frequencies and weak peaks at lower frequencies induced by the incorporation of the Ho3+ and Yb3+ elements into the Y3+ site in the crystal lattice, which resulted in the unit cell shrinkage accompanying the new phase formation of the [WO4](2-) groups. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.