Synthesis of yttria nano-powders by the precipitation method: The influence of ammonium hydrogen carbonate to metal ions molar ratio and ammonium sulfate addition

Yttria (Y 2 O 3 ) nano-powders were synthesized by the normal-strike precipitation method. The influences of R (NH 4 HCO 3 /M 3+ , molar ratio) and ammonium sulfate addition were studied throughout the preparation process. Several analytic techniques such as XRD , TG/DSC, SEM and FTIR were used to determine the characteristics of the precursors and Y 2 O 3 powders. It was found that morphologies and phases of the precursors were evidently influenced by the R value. The phases of the precursors were Y 2 (CO 3 ) 3 ·2.79H 2 O when R was 3–4, while the composition of the precursors with R = 4–5 was (NH 4 ) a Y(OH) b (CO 3 ) c ·xH 2 O. Homogeneous needle-flake shaped particles composed of coadjacent grains with diameters of about 70 nm were obtained as the R = 3–4. The rhombohedral flake-shaped particles were the products with R = 5–6. The mechanism of the influence of R value on the precipitation of the precursor was also investigated in this work. Pure Y 2 O 3 nano-powders were obtained by calcining the precursors at 1000 °C for 4 h regardless of what the R value was. Sulfate ions affect not only dispersion of nanopowders, but also their grain size. Results obtained in this work are contributed to the controllable synthesis of yttria powders.