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Controlled synthesis and luminescence properties of doped NaLa(WO4)2 microstructures
Yunhua Han,Yan Wang,Shaohua Huang,Fan-Long Jin,Shili Gai,Na Niu,Liuzhen Wang,Piaoping Yang 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.34 No.-
In this work, well-defined NaLa(WO4)2microstructures were prepared by a facile hydrothermal processin the presence of oleylamine and oleic acid as a mixed surfactant. The phase, morphology, size andluminescence properties were well characterized by means of X-ray diffraction (XRD), scanning electronmicroscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and decaytime, respectively. The results reveal that the morphology and size of the as-synthesized samples can betuned by altering the reaction time and the amounts of oleic acid. A possible formation mechanism oftetragonal NaLa(WO4)2 is proposed on the basis of oleic acid amount-dependent experiments. Uponultraviolet (UV) excitation, NaLa(WO4)2:Eu3+ and NaLa(WO4)2:Tb3+ exhibit the characteristic downconversionemissions of Eu3+ and Tb3+. Yb3+/Er3+ and Yb3+/Tm3+ co-doped NaLa(WO4)2 samples showstrong green (Er3+, 4S3/2, 2H11/2!4I15/2) and blue (Tm3+, 1G4!3H6) up-conversion emission under980 nm laser diode excitation. Upconversion emission mechanisms of NaLa(WO4)2:Ln (Ln = Yb/Er, Yb/Tm) are also presented based on the emission spectra and the plot of luminescence intensity to pumppower. It should be noted that the intensity of the upconversion emissions can be dramatically enhancedcompared with sodium free tungstates, which can be attributed to the charge compensation and meansthe introduction of Na+ ions in WO42 causes less distortion in the crystal structure.