Citrate-nitrate synthesis and understanding the properties of yttrium orthoaluminate-based luminophors

Abstract

Using citrate-nitrate sol gel method, the authors obtained yttrium orthoaluminate with a perovskite structure YAlO3, as well as luminophors containing europium (III) ions Y1–хEuxAlO3 (x = 0.01; 0.025; 0.050; 0.075; 0.1). The conducted study helped understand the dynamics of phase and structural transformations that take place during yttrium orthoaluminate synthesis. Methods of thermal and X-ray phase analysis were used to establish the key stages of the synthesis process, and the Rietveld method based on ReX Powder diffraction software was used for quantitative evaluation. At the final process stage, sol forms, which then converts into gel and, when dried, forms xerogel. Heat treatment of xerogel leads to the decomposition of the organic framework and production of gaseous products. The solid phase interaction that takes place during YAlO3 synthesis involves stages at which yttrium – aluminium oxycarbonate Y3Al3O8CO3, as well as yttrium aluminates Y4Al2O9 and Y3Al5O12 form. Annealing at 1,300 oC for 7 hours enables to achieve the maximum concentration of orthoaluminate – i.e. 83% wt. Introduction of europium (III) ions stabilizes the perovskite structure, and the mass fraction of YAlO3 in the final product rises as the concentration of europium(III) ions rises. The maximum concentration of the target phase is 96 wt.%, achieved when 0.1 mol Eu3+ is introduced into the matrix. The surface morphology of yttrium aluminate was studied by scanning electron microscopy. Particles of similar grain size and shape can be obtained when conducting the synthesis at 1,300 oC. The authors examined the luminescence properties of yttrium orthoaluminate-based crystalline phosphors. Luminophors containing Eu3+ ions and having the following composition: Y1–хEuхAlO3 (x = 0.01; 0.025; 0.050; 0.075; 0.1), emit red light, which is typical of Eu3+ in crystal matrices. The Y0,9Eu0,1AlO3 luminophor has the maximum emitted intensity. Support for this research was provided under the Development Programme of the Tomsk State University Priority 2030.