Upconversion Photoluminescence Properties of KGd(WO4)(2): Ho3+/Yb3+ Phosphors Synthesized by Microwave-assisted Sol-Gel Method

摘要

Double tungstate KGd1-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- assisted sol-gel method, and the upconversion (UC) mechanisms by a two-photon process have been investigated in detail. Well-crystallized particles, formed after heat-treatment at 900 degrees C for 16 h, showed a fine and homogeneous morphology with particle sizes of 2-10 mu m. Under excitation at 980 nm, the UC intensities of KGd0.7(WO4)(2): Ho0.1Yb0.2 and KGd0.5(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-5(2)/F-5(4) -> I-5(8) and F-5(5) -> I-5(8) transitions, respectively. The Raman spectra of the particles indicated the appearance of strong peaks at higher frequencies (1050, 1106, 1250, and 1340 cm(-1)).