【作者】 吴燕利；

【导师】 李永绣；

【作者基本信息】 南昌大学 ， 无机化学， 2006， 硕士

【摘要】 本论文采用氧化物水化法、草酸铵沉淀法和碳酸盐水热法来合成具有特殊形貌的稀土氢氧化物、草酸钇（铕）铵复盐和碳酸钕结晶，并经高温煅烧得到相应的稀土氧化物。用X-射线衍射（XRD）、扫描电镜（SEM）、透射电镜（TEM）、光致荧光光谱（PL）及元素分析等技术研究了结晶产物的物相、外观形貌、化学组成和荧光性质。结果表明： 1．氧化镧、氧化钆、氧化钇与水直接反应形成氢氧化物的能力有很大差别。氧化镧的水化能力最强，用常压沸腾水化处理制备了具有棒状外型的六方相氢氧化镧，其直径为2-3μm，长为5-8μm。氧化钆在水热条件下可与水反应形成氢氧化钆，但速度慢，增加水热处理时间或添加适量碱，可以促进氢氧化钆的形成，得到类似于泡泡果的微米和亚微米级的棒状氢氧化钆。氧化钇在水热条件下不与水直接反应形成氢氧化钇，但在碱性溶液中水热处理可以得到剑形棒状的氢氧化钇。这些棒状氢氧化物在高温下的煅烧产物仍保持棒状结构，说明热分解对产物形貌没有明显改变。 2．氧化钇在含PVA或PEG的碱性溶液中水热处理，得到了管状氢氧化钇，其内径为50nm左右，外径为100—200nm之间，长度为几个微米，管口呈六角形。颗粒表面光滑，分散性好，尤其是在PVA存在下所得的产品管径比更大。 3．氢氧化钇的取向生长特性归因于六方晶体结构的各向异性，在碱性溶液中水热处理得到的是氢氧化钇棒。在表面活性剂存在下，加速了沿纳米棒表面水平方向的生长速度，而中心部位的生长速率小，促进了氢氧化钇纳米管的形成。 4．Y₂O₃：Eu纳米管的激发光谱除在240nm处的强峰外，在226nm处出现了另一个强峰，认为是由于Eu³⁺处于Y₂O₃：Eu纳米管的管内和管外时所处的微环境不同所致。其发射光谱为典型的⁵D₀-⁷F_j（j=0，1，2，3，4）的跃迁发射。611nm处的最强峰是由于强制偶极跃迁（⁵D₀-⁷F₂）。 5．通过草酸钇（铕）铵复盐途径制备得到了Y₂O₃：Eu纳米片和块。在pH6.0-7.5范围内沉淀，经800℃煅烧制备出平面尺度在0.6到1.5μm，厚度为50nm左右的Y₂O₃：Eu纳米片。而分解由氢氧化钇转化而来的草酸钇铵复盐可以得到边更多还原

【Abstract】 Rare earth （lanthanum, gadolinium and yttrium） hydroxides, ammonium yttrium oxalate and neodymium carbonates were synthesized by the hydration of rare earth oxides, the precipitation of yttrium with ammonium oxalate and the hydrothermal crystallization of neodymium carbonate respectively. Their morphologies and property were evaluated using XRD, SEM, TEM, PL and elemental analysis technologies. The main achievements include:[1] The hydration of La₂O₃、Gd₂O₃ and Y₂O₃ showed great difference due to their differences in basicity, ionic radius, and crystal structure. It was found that the La₂O₃ was hydrated to form rodlike La（OH）₃ with diameter 2-3μm,length 5-8μm at mild conditions （billing water temperature and ambient pressure） directly. Gd₂O₃ can also be hydrated to form Gd（OH）₃ under hydrothermal condition. However, Gd（OH）₃ with unusual fluffy dough sticks morphology was formed after hydrothermal treating its oxide with longer time or in NaOH solution. Y₂O₃ could not be hydrated in normal water. Sword-like Y（OH）₃ was obtained by the hydrothermal reaction in basic solution with prolonging time. Upon heating these hydroxides transformed into oxides with no evident morphology change, indicating that the rare earth oxides materials with special morphology could be prepared via their intermediate hydroxide.[2] Hexagonal tube-like Y（OH）₃ with inner diameter about 50nm、external diameter 100-200nm was prepared by hydrothermal treating Y₂O₃ in NaOH solution with additive of PVA or PEG.. The tube particles show smooth surface and disperse well. The relative elongation （ratio of the length of the long to the diameter） increased with the addition of surfactants, especially for the addition of PVA. It was the anisotropic crystal structure of La（OH）₃, Gd（OH）₃ and Y（OH）₃ that resulted in the formation of these hydroxides with one dimension crystal growth characteristics. The addition of surfactants should be favorable for the crystal growth along the surface horizontal direction due to the selection adsorption of surfactants on the crystal plane. However, the crystal growth from the middle position of a bar was slow down due to the limit of material diffusion, which resulted in the formation of tube morphology.[3] The excitation spectrum of Y₂O₃:Eu shows an unusual strong excitation peak at 226nm except for the charge transfer band at around 240nm, which might be更多还原