Control of structure and morphology of starting nanopowders is an important technological task in formation of novel consolidated materials for functional applications. In particular, obtaining of low agglomerated nanopowders of rare earth oxides with controlled morphology is of significant interest for the development of laser ceramics for the new generation of solid-state lasers.

One of the ways of solving this problem in the framework of the traditional method of chemical precipitation is an introduction of some additives into the reaction mixture which modifies in some way the charge state of synthesized particle surfaces. The purpose of such modification is to provide formation of double charged layer onto the surface of each particle and, consequently, to increase the repulsion forces between the particles and prevent their agglomeration during thermolysis of the precursor. It was recently reported that sulfate ions promote formation of monodisperse quasy-spherical nanosized oxide powders and hinder their agglomeration. We have previously shown that introduction of sulfate ions into reaction mixture allows one to produce low agglomerated Y₃Al₅O₁₂ nanopowders with quasy-spherical morphology of particles [1]. Despite some reports on improving the morphology, particle size, and agglomeration degree of precipitated Y₂O₃ nanopowders via sulfate ions introduction, the role of sulfate ions is not well understood. The purpose of this work is to study the effect of sulfate ions on the structural and morphological characteristics of precipitated Y₂O₃ nanopowders, a promising material to be used as structural elements of yttrium aluminum garnet laser ceramics.

Sulfate-stabilized Y₂O₃ nanopowders were produced by chemical precipitation. The evolution of phase composition, specific surface area, crystallite size and morphology of Y₂O₃ nanopowders during thermal annealing of the precursor in the 600-1300°C temperature range has been studied by means of XRD, DTA-TG, BET methods and FT-IR spectroscopy. It has been found that the presence of residual SO₄^2--ions on the surface of the particles provide nearly equal growth rate of different crystallographic planes of Y₂O₃, resulting in a nearly spherical particle morphology and prevents their agglomeration at the stage of thermal annealing of the precursor up to 1200°C. It has been shown that Y₂O₃ stabilized nanopowders have a higher sinterability than non-stabilized ones, which allow one to consider them as a prospective component for obtaining of YAG laser ceramics by reaction sintering.

References:

[1]       T.G. Deineka et al., J. Alloys Compd., 508, 200-205 (2010).

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