材料期刊网

以草酸铵为沉淀剂, 以尿素为pH调节剂, 以Ce(NO₃)₃ ?6H₂O、Ca(NO₃)_2? 4H₂O、Sm₂O₃和Gd₂O₃为起始原料, 采用改进的均相沉淀法合成前驱物, 将其在700℃焙烧4.5 h, 分别制备出Ca掺杂及Ca--Sm和Ca--Gd复合掺杂的CeO₂ 基纳米粉体. 用X射线衍射(XRD)、扫描电子显微镜(SEM)和BET法等技术对焙烧粉体的物相、形貌、晶粒尺寸及比表面积进行了分析表征. 结果表明, 当混合金属离子的总浓度为0.5 mol/L、沉淀剂浓度为0.05 mol/L、起始水解pH值为1时, 可制备出具有立方萤石型晶体结构及良好结晶性、粒度分布在34--39 nm之间的球形纳米粉体. 采用乙醇分散和洗涤掺杂前驱体沉淀, 能有效地减轻焙烧粉体的团聚程度.

Ceria–based precursors doped with calcium, calcium–samarium and calcium–gadolinium were prepared by an improved homogeneous precipitation method using ammonium oxalate as precipitant, high purity reagents Ce(NO₃)₃·6H₂O, Ca(NO₃)₂·4H₂O, Sm₂O₃ and Gd₂O₃ were used as raw materials, urea was used as pH adjuster of the mixed solution. The as–synthesized precursor were calcined at 700 ℃ for 4.5 h. The calcined powders were characterized by X–ray diffraction (XRD), scanning electron microscopy(SEM), and Brunauer–Emmett–Teller(BET) specific surface area measurements. The results show that the calcined powders have satisfactory characterizations when the initial hydrolysis pH is approximately 1, the total concentration of mixed cation ions is 0.5 mol/L, and the initial concentration of precipitant is 0.05 mol/L. The powders after calcined have a single cubic fluorite crystalline structure and higher phase purity, with spherical nano–sized particles about 34–39nm in diameter and narrow size distribution. In this study, doped ceria precursors were redispersed and washed in ethanol can alleviate the degree of agglomeration of the calcined powders.