Mechanism of ammonium sulfate regulation effect on microstructure of Y2O3 nanopowders via urea precipitation method

Abstract

In the preparation of transparent ceramics and ultrafine oxide nanopowders, ammonium sulfate ((NH₄)₂SO₄) has been widely used as the control agent. However, the mechanism of its regulation effect has not been well studied. In the present work, precursors of yttria (Y₂O₃) nanopowders with controlled morphology were synthesized via a urea precipitation method using ammonium sulfate as the additive. The effect of (NH₄)₂SO₄ is discussed throughout the preparation process. Two opposite morphology transformation modes were noticed for the precursor samples made with and without (NH₄)₂SO₄ during the calcination process. Flocculent precursors and flowers assembled by the plate-shaped particles were obtained in the systems without and with (NH₄)₂SO₄. By calcination, the aggregated 200–400 nm particles with massive defects and 100 nm particles with homogeneous crystalline structure were obtained, respectively. The mechanism of (NH₄)₂SO₄ as a regulator that could mediate the nucleation and growth of the precursors as well as its decomposition behavior is verified.