改进的碳铵沉淀法中氧化钇粉体尺寸及形貌的调控研究

以商业氧化钇(Y2O3)为原材料,采用改进的碳酸盐沉淀工艺合成钇碳酸盐前驱体,经随后的焙烧工艺获得Y2O3产品。X衍射技术(XRD)和扫描电镜(SEM)表征表明:合成的碳酸盐前驱体Y2(CO3)3·2H2O具有类球形形貌、粒度分布均匀,经950℃焙烧2h,前驱体受热分解为Y2O3粉体,粉体完整保留了前驱体的形貌特征。同时,基于对NH4HCO3/NH+4不同摩尔比条件下NH4HCO3/NH4NO3混合溶液中pH值变化的理论计算,在保持其他条件不变化条件下,通过改变NH4HCO3/NH4NO3混合溶液的加入量以获得不同的稀土碳酸盐沉淀终点pH值,当碳酸盐沉淀过程中pH值从6.0降低至4.7时,可实现超细至大颗粒不同尺寸氧化钇粉体的制备。同时,公斤级的扩大试验证实该工艺具有良好的可推广性。进一步提出NH+4在碳酸氢铵沉淀制备氧化钇工艺中的作用机理:(1)改变反应体系中阳离子和阴离子的组成;(2)显著影响前驱体的晶型;(3)显著影响产品颗粒尺寸大小。

Size and Morphology Control of Y2 O3 Powders by Improved Ammonium Bicarbonate Precipitation Method

Well-dispersed Y2O3 powders were synthesized by mean of an improved ammonium bicarbonate precipitation method and subsequent calcination treatment. Raw materials used were commercially available yttrium oxide( Y2O3). X-ray powder diffraction( XRD) and scanning electron microscopy( SEM) results reveale that the as-formed precursors Y2( CO3)3·2 H2 O with tengerite type structure were decomposed into Y2O3 while heated,which well inherited the morphological characteristic of the precursor after calcination at 950 ℃ for 2 h. Meanwhile,based on the results from theoretical calculation of the p H value varying from NH4+/HCO3-molar ratios in NH4HCO3/NH4NO3 mixed solution,experiments carried out were by mainly adjusting the adding amount of NH4HCO3/NH4NO3 so as to profoundly investigate the effect of p H value on the size and morphology of the final Y2O3 particles. It’s found that the size and morphology could be remarkably affected by the final p H value during the liquid phase reaction process. The final products Y2O3,varied in different sizes ranging from micrometer to nanoscale,were obtained when the p H value was adjusted from 6. 0 to 4. 7,while keeping the other parameters unchanged.More intriguingly,the result obtained from the kilo-scale expanding test under the optimal synthesizing parameters above shows that the adaptability of the process is excellent. Furthermore,the action mechanism of NH4+in the preparation of final products Y2O3 were properly proposed:( 1) to change the combination of the cations and different anions;( 2) to exert significant impact on the crystal of the precursor;( 3) to greatly affect the final product particle size.