Multicolor Upconversion Emission and Color Tunability in Tm3+/Er3+/Yb3+ Tri-Doped NaNbO3 Nanocrystals
The Tm3+/Er3+/Yb3+: NaNbO3 nanocrystals (NCs) were synthesized using sol–gel method and the nanocrystallite sizes of about 70 nm were estimated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results of the XRD revealed that the powders remained as a single orthorhombic structure at doping concentrations below 7.5% of Yb3+. A second phase of YbNbO4 begins to appear at 10%. Studies of photoluminescence properties with respect to ion concentration as well as laser pump power were carried out. The upconversion (UC) emission spectra of NCs show white luminescence and color tunability composed with multicolor combination of red, green and blue emissions under excitation at 970 nm. The red and green UC is consistent with 4F9/2 → 4I15/2 and 2H11/2, 4S3/2 → 4I15/2 transition of Er3+ ions, while the blue and near infrared (800 nm) UC originate from 1G4 → 3H6 and 3H4 → 3H6 transitions of Tm3+ ions, respectively. Change in UC luminescence intensity and multicolor tunability with respect to Ln3+ concentration as well as pump powers in Tm3+/Er3+/Yb3+ tri-doped NaNbO3 NCs were discussed and calculated the CIE color coordinates as well. From the present results we point out the direction to tailor the system for an efficient white light generation.
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Document Type: Research Article
Publication date: 2012-12-01
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