Yttrium oxide nanopowders from carbonate precursors

Reactions of solutions of yttrium oxide in nitric acid with a 1.67 M NH 4 HCO 3 solution were studied by direct and back titration. When the concentration of the reacting solution was within 0.031–0.052 mol/L (as Y 2 O 3 ), yttrium carbonate Y 2 (CO 3 ) 3 · n H 2 O ( n ≈ 2.5) of fibrous or spherulitic morphology precipitated. When the concentration was decreased to 0.022 mol/L, a new phase of platy morphology appeared. Heating these precipitates to 650–680°C yielded yttrium oxide having coherent scattering domain sizes of 40–80 nm. Y 2 O 3 particles retain the precursor morphology.