Bi系超导材料的Sol-Gel法制备、机制及掺杂研究

发布时间：2018-03-05 18:20

  本文选题：Bi系超导材料　切入点：Sol-Gel法　出处：《东北大学》2010年博士论文　论文类型：学位论文

【摘要】：本文以可溶性金属硝酸盐为原料,乙二胺四乙酸为络合剂,采用Sol-Gel法制备Bi系氧化物粉体及薄膜。通过对Sol-Gel法凝胶工艺的优化,改进粉体相纯度及结晶性；并在此基础上进行了Bi位La微掺杂Bi-2212粉体及Sr位Ca掺杂Bi-2201粉体的掺杂效应研究；最后,将较佳的粉体制备工艺应用于Bi-2212薄膜的制备。本文具体研究内容如下： 1.分别采用Sol-Gel法与PSG法(Pechini型Sol-Gel法)制备Bi-2212粉体材料,分析凝胶化工艺对超导粉体质量的影响。实验结果表明,合适的凝胶化过程能够明显增强凝胶网络强度,减少凝胶中游离金属离子的数量,改善金属离子均一性,从而提高Bi-2212粉体的相纯度及结晶性。同时,合适的凝胶工艺对保持各金属元素的比例具有重大意义。由于各金属离子分布更加均匀、自发燃烧过程中金属硝酸盐分解的更加充分,粉体烧结性得到改善,因此烧结时间由10h减短至5h,可节约大量能源。 2.采用Sol-Gel法细致研究了Bi位La微掺杂Bi-2212粉体结构及电学性能变化,La掺杂x范围为0.01-0.09。利用TG-DTA曲线对化学反应过程进行分析,利用X射线衍射进行相分析,利用标准四引线法测试电学特性随温度变化曲线(R-乃。实验结果表明,掺La后Bi-2212粉体相仍保持正交结构,但随着La掺杂量的增加,a、b轴长度增加,c轴长度减小。并且,La的掺杂虽然并未发生在CuO2面上,但却影响着Cu02面的电子性质,对Bi-2212相的导电特性影响显著。 3.采用PSG法制备Sr位Ca掺杂Bi-2201粉体,并对Bi-2201相结构及电学性能进行分析、表征。实验结果表明,掺Ca后Bi2Sr2-xCaxCuOy相的较佳烧结温度随着x值的变化而变化。Ca掺杂量在0.6≤x0.7达到最大,同时样品的晶胞参数a,b,c均随着x值的增加而减小。根据R-T测试结果可知,Ca的掺杂可将Bi-2201相的超导转变温度Tc提高至86K。根据这一实验结果,本文提出了Bi-2201相结构变化模型,用以解释Bi2Sr2-xCaxCuOy相Tc的提高。 4.采用PSG法在STO衬底上制备具有c轴外延取向的Bi-2212薄膜。通过对Bi系超导粉体制备工艺的细致研究,得出高质量Bi系粉体的制备方法,并将此方法应用于Bi-2212薄膜的制备。通过对薄膜制备工艺的细致研究得出具有较高质量的、c轴外延取向的Bi-2212薄膜。实验结果表明,溶胶成分为Bi2Sr2Ca1.05Cu2O8+δ、薄膜经150℃-190℃预处理、经835℃烧结10min所得到的的Bi-2212薄膜具有较高的相纯度及较平整、连续的表面形貌。通过对薄膜的电学性能分析得出,不同制备条件对薄膜的Tc,onset影响较小,但Tc,0变化较大。
[Abstract]:In this paper, Bi based oxide powders and thin films were prepared by Sol-Gel method using soluble metal nitrate as raw material and ethylenediamine tetraacetic acid as complexing agent. The phase purity and crystallinity of the powders were improved by optimizing the gel process of Sol-Gel method. On this basis, the doping effect of Bi-La micro-doped Bi-2212 powder and Sr-Ca-doped Bi-2201 powder was studied. Finally, the better preparation technology was applied to the preparation of Bi-2212 thin film. 1. Bi-2212 powder materials were prepared by Sol-Gel method and Pechini type Sol-Gel method respectively. The effect of gelation process on the quality of superconducting powder was analyzed. The experimental results show that the gel network strength can be significantly enhanced by proper gelation process. Reducing the amount of free metal ions in gel, improving the homogeneity of metal ions, thus improving the phase purity and crystallinity of Bi-2212 powder. The proper gel process is of great significance to maintain the proportion of metal elements. As the distribution of metal ions is more uniform and the decomposition of metal nitrate is more adequate during spontaneous combustion, the sintering properties of the powders are improved. Therefore, the sintering time is reduced from 10 h to 5 h, which can save a lot of energy. 2. The structure and electrical properties of Bi-La microdoped Bi-2212 powder were studied by Sol-Gel method. The range of La doping x was 0.01-0.09.The chemical reaction process was analyzed by TG-DTA curve and the phase was analyzed by X-ray diffraction. The standard four-lead method was used to measure the electrical properties of Bi-2212 powder with temperature. The experimental results showed that the phase of Bi-2212 powder remained orthogonal structure after La doping. However, with the increase of La doping amount, the C axis length decreases with the increase of La doping content, and La doping does not occur on the CuO2 surface, but it affects the electronic properties of the Cu02 plane, which has a significant effect on the conductivity of the Bi-2212 phase. 3. Sr Ca doped Bi-2201 powders were prepared by PSG method, and the phase structure and electrical properties of Bi-2201 were analyzed and characterized. The experimental results showed that the optimum sintering temperature of Bi2Sr2-xCaxCuOy phase changed with the change of x value. The content of Ca doping reached the maximum at 0.6 鈮，

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