Investigation of lanthanum substitution effects in yttrium aluminium garnet: importance of solid state NMR and EPR metho
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ORIGINAL PAPER: SOL-GEL, HYBRIDS AND SOLUTION CHEMISTRIES
Investigation of lanthanum substitution effects in yttrium aluminium garnet: importance of solid state NMR and EPR methods A. Laurikenas1 D. Sakalauskas1 A. Marsalka2 R. Raudonis1 A. Antuzevics3 V. Balevicius2 A. Zarkov1 A. Kareiva 1 ●
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Received: 17 August 2020 / Accepted: 15 November 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract In this study, yttrium aluminium garnet (YAG) specimens in which yttrium was partially substituted by lanthanum Y3-xLaxAl5O12 (YLaAG) were prepared by an aqueous sol-gel method. YLaAG samples were analyzed by X-ray diffraction (XRD), solid state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) methods. The presence of Ce3+ ions as an impurity originating from starting material was determined, therefore, luminescence measurements of YLaAG samples were also recorded. It was demonstrated that luminescent properties are strongly dependent on the phase composition of synthesized species. The XRD analysis results showed that only low substitution of yttrium by lanthanum is possible in Y3-xLaxAl5O12 without destroying garnet crystal structure. It was also demonstrated, that solid state NMR and EPR methods are indispensable tools for the explanation of processes and properties observed in the newly synthesized Y3-xLaxAl5O12 compounds. Graphical Abstract
Keywords
Yttrium aluminium garnet Lanthanum Substitution effect NMR EPR ●
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* A. Kareiva [email protected] 1
Institute of Chemistry, Vilnius University, Naugarduko 24, LT-03225 Vilnius, Lithuania, 03225 Vilnius, Lithuania
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Institute of Chemical Physics, Faculty of Physics, Vilnius University, Saulėtekio al. 3, LT-10257 Vilnius, Lithuania
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Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga, Latvia
Journal of Sol-Gel Science and Technology
Highlights ● Y3-xLaxAl5O12 specimens were synthesized using aqueous sol-gel synthesis method. ● Monophasic garnets obtained at low substitution of yttrium by lanthanum. ● The region of coexisting phases have been evidently deduced by solid state NMR spectroscopy. ● The Ce3+ emission at around 560 nm was observed in Y3-xLaxAl5O12 garnets. ● The EPR analysis provided experimental evidence for the presence of Ce3+ impurities in the samples.
1 Introduction Yttrium and lanthanide aluminium garnets (Y3Al5O12, YAG and Ln3Al5O12, LnAG, Ln—lanthanide element from Eu to Lu) show great chemical stability, high temperature creep resistance and extremely important luminescent properties [1–6]. However, during the preparation of YAG the formation of secondary phases like perovskite (YAlO3, YAP) and monoclinic aluminate (Y4Al2O9, YAM) very often have been observed [7, 8]. The solgel techniques have been used to prepare a variety of mixedmetal oxides including garnet materials with excellent phase purity of the final product [9–13]. Several lanthanide aluminium garnets (i.e., La3Al5O12, Ce3Al5O12, Pr
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