Synthesis of silicate apatite phosphors with enhanced luminescence via optimized precipitation technique through pH cont
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O R I G I N A L P A P E R : S O L - G E L A N D H Y B R I D M A T E R I A L S F O R O P T I CA L , PHOTONIC AND OPTOELECTRONIC APPLICATIONS
Synthesis of silicate apatite phosphors with enhanced luminescence via optimized precipitation technique through pH control I. Perhaita1 L. E. Muresan ●
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L. Barbu Tudoran2,3 D. T. Silipas3 G. Borodi3 ●
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Received: 28 May 2020 / Accepted: 20 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Silicates with apatite structure have become one of the most promising candidates for solid-state lighting applications. Herein we report the synthesis of pure apatite Ca2Y7.76Ce0.12Tb0.12(SiO4)6O2 phosphors with enhanced luminescence via a simple precipitation method. The aim of this study is to optimize the precipitation reaction through pH control and TEOS amount. In this respect, different types of precursors were prepared by precipitation between yttrium–calcium–cerium–terbium nitrates and NaOH at various pH. The extremely complex decomposition processes of precursors are discussed based on thermogravimetric analysis. The structure, morphology, surface state and porosity of both precursors and phosphors were investigated based on FTIR, XRD, SEM and BET. It was found that the crystallinity degree of the precursors decreases from 36% to 5% with the increase of pH from 7 to 11. After the thermal treatment, the phosphors become pore-less and well crystallized with crystallite sizes up to 106 nm. The phase composition of the phosphors strongly depends on the pH during the precipitation. Synthesis performed with 40% excess of TEOS at pH 11 led to phosphors with pure apatite structure and enhanced luminescence. Under excitation with 365 nm the apatite phosphors exhibits a broad emission band in the range of 350–480 nm, due to transitions in Ce3+ and narrow lines in range of 480–650 nm specific for transitions in Tb3+. Graphical Abstract
Supplementary information The online version of this article (https:// doi.org/10.1007/s10971-020-05400-1) contains supplementary material, which is available to authorized users. * L. E. Muresan [email protected] 1
Raluca Ripan Institute for Research in Chemistry, Babes- Bolyai University, Fantanele 30, 400294 Cluj-Napoca, Romania
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Electronic Microscopy Centre, Babes- Bolyai University, Clinicilor, 5-7, 400006 Cluj-Napoca, Romania
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National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj Napoca, Romania
Journal of Sol-Gel Science and Technology
Keywords
Silicate apatite Luminescence Precipitation Effect of pH Rare earth ●
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Highlights Gel precursors are prepared by precipitation at different pH for synthesis of apatite phosphors. ● pH affects the morpho-structure and surface state of both precursors and phosphors. ● Pure apatite with crystallites size of 66.5 nm was obtained at pH 11. ● Effect of pH on Ce3+ and Tb3+ emission intensities was discussed in detail. ● Apatites show blue, white-turq
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