Upconversion fluorescence in Nd 3+ /Yb 3+ co-doped titanate glasses prepared by containerless method
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anding Yu Japan Aerospace Exploration Agency, ISS Science Project Office, Tsukuba 305-8500, Japan
Yan Liu and Minghui Zhang State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China (Received 24 March 2011; accepted 26 September 2011)
Nd3+/Yb3+ co-doped TiO2–La2O3 glasses modified by ZrO2 were fabricated by containerless method. Under the excitation of 980 nm lasers, three intense emissions centered at 521, 545, and 655 nm were observed, which are assigned to the Nd3+: 4G9/2/4I9/2, 4G7/2/4I9/2, and 4 G7/2/4I13/2 transitions, respectively. Besides, two very weak emission bands at 496 and 603 nm were also found due to the Nd3+ transition of 2G9/2/4I9/2 and 4G5/2 (or 2G7/2)/4I9/2, respectively. Pumping powder dependence of emission intensity suggests a two-photon adsorption process responsible for the upconversion luminescence. A combined phonon-assisted and cooperative sensitization mechanism is presented to interpret the energy transfer from Yb3+ to Nd3+ ions. In addition, the highest intensity of luminescence was found for the glass with 1.2 mol% Nd3+, and the upconversion efficiency can be enhanced by increasing of ZrO2 content.
I. INTRODUCTION
Upconversion of light from infrared to visible wavelength in rare earth (RE) ions-doped glasses attracted much attention because of their potential use in infrared converters and upconversion short wavelength solid-state lasers.1,2 The trivalent neodymium ion (Nd3+) is one of the most important active ions in the RE family due to its favorable energy level structure. Spectroscopic results demonstrate that the Nd3+ ions are good candidates for upconversion luminescence.3,4 Usually, host materials with low phonon energy are in favor of strong upconversion luminescence because it can reduce the nonradiative loss caused by the multiphonon relaxation. Recently, sincere attention has been focused on the development of Nd3+-doped low phonon glasses (like antimonate, germanate, tellurite, and fluoride glasses), which display efficient upconversion of the infrared into visible light.5–10 Titanium dioxide can be a good candidate for upconversion generation due to its low cutoff phonons of energy (;600–700 cm 1).11,12 However, to the best of our knowledge, there is no report dealing with the upconversion fluorescence characteristic of Nd3+-doped TiO2-based glasses, mainly due to the difficulty of titanate glass formation by traditional melt-quenching method. a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.365 J. Mater. Res., Vol. 26, No. 23, Dec 14, 2011
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In this article, we report the fabrication of Nd3+doped high titanium dioxide (;80 mol%) containing La2O3–ZrO2–TiO2 (LZT) glasses by containerless processing in an aerodynamic levitation furnace (ALF). The upconversion property sensitized by Yb3+ ion is investigated with special emphasis. The purpose of this investigation is to dev
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