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The crystallization and morphological evolution of yttrium carbonate when aging at 50 ℃ after its precipitation by ammonium bicarbonate with feed molar ratio NH4HCO3∶YCl3=2 were investigated by means of XRD, SEM and pH situ-determination. It was found that pH value and deposit volume of the solution all deceased in a two-step manner during aging. Correspondingly, the spherulitic needle-aggregate yttrium carbonate formed initially was transformed into 2-D flake and 3-D regulate grain particles. However, X-ray patterns of all the crystalline yttrium carbonates are identified with the structure of tengerite Y2(CO3)3·2H2O. These facts demonstrate that the crystallization of yttrium carbonate follows Oswald′s rule of stages that the final stable morphology of crystalline yttrium carbonate is transformed from 1-D to 2-D, and then to 3-D by two or more steps through the mechanism of dissolution-recrystallization. A fast crystallization method of yttrium carbonate with large particle size was proposed.
The crystallization and morphological evolution of yttrium carbonate when aging at 50 ℃ after its precipitation by ammonium bicarbonate with feed molar ratio NH4HCO3:YCl3 = 2 were investigated by means of XRD, SEM and pH situ-determination. It was found that pH value and deposit volume of the solution all deceased in a two-step manner during aging. Correspondingly, the spherulitic needle-aggregate yttrium carbonate formed initially was transformed into 2-D flake and 3-D regulate grain particles. However, X- ray patterns of all the Crystalline yttrium carbonates are identified with the structure of tengerite Y2 (CO3) 3 · 2H2O. These facts demonstrate that the crystallization of yttrium carbonate follows Oswald’s rule of stages that the final stable morphology of crystalline yttrium carbonate is transformed from 1-D to 2-D, and then to 3-D by two or more steps through the mechanism of dissolution-recrystallization. A fast crystallization method of yttrium carbonate with large particle si ze was proposed.