| Summary: | In this study, a CO<sub>2</sub> carbonization method is introduced for the preparation of 1D yttrium oxide powders. Using YCl<sub>3</sub> as the raw material, sodium hydroxide was initially used to completely precipitate Y<sup>3+</sup> into yttrium hydroxide, and then CO<sub>2</sub> was introduced into the yttrium hydroxide slurry for homogenization-like carbonization to obtain yttrium carbonate precipitation. Then, by studying the effects of carbonization conditions, such as the temperature, CO<sub>2</sub> flow rate, and stirring speed, on the morphology and phases of yttrium carbonate, the temperature was observed to exert a greater effect than the other experimental parameters on the morphology and structure of the carbonized products. Finally, Y<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub>·2H<sub>2</sub>O nanoneedles were obtained at optimal conditions. The carbonized crystals of the acicular yttrium carbonate precipitate because of the solution supersaturation and then quickly complete their crystal growth process through the oriented attachment (OA) and Ostwald ripening (OR) mechanisms. After heat treatment, yttrium carbonate retained a good crystal morphology and produced Y<sub>2</sub>O<sub>3</sub> nanoneedles with a length of 1–2 μm and a width of 20–30 nm.
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