YBa₂Cu₃O_7-d及元素替代材料的透氧性能研究

【作者】 宋红章；

【导师】 杨德林；

【作者基本信息】 郑州大学 ， 凝聚态物理， 2005， 硕士

【摘要】 本文首先介绍了混合导体透氧膜的概念、种类、研究进展、透氧机理及透氧率的理论公式。较全面地论述了透氧膜的制备方法、性能表征、应用情况及当前发展中存在的一些问题。并描述了高温超导材料YBa₂Cu₃O_7-δ（简写:YBCO）的发现过程、结构特点及各种氧特性。 用暂态热重法研究分析了YBCO在不同的温度下N₂→O₂→N₂交变气流中的吸氧、脱氧过程,估算了其在不同温度下的氧吸附速率、氧脱附速率。结果表明,在暂态测试条件下,YBCO对氧有强烈的选择吸附性,并且吸氧、脱氧过程是可逆的,氧吸附过程较迅速,而氧脱附过程则较缓慢;氧吸附或氧脱附过程仅在开始段是表面扩散,以后体扩散开始起作用,并在YBCO热重曲线的平缓阶段处于主导地位。用热重法研究了BaRE(Cu_0.5Fe_0.5)₂O_5+δ（RE=Lu～Pr）样品的氧含量的变化。结果表明仅RE=Pr、Nd、Gd时样品的氧含量随温度和氧分压变化而变化,其它样品的氧含量基本不发生变化。用暂态热重法估算的RE=Pr、Nd、Gd样品的表面反应速率和氧渗透通量比YBCO的明显较低。 用稳态法（色谱分析法）研究了各种厚度的YBCO透氧膜在不同温度下的透氧率。膜的高氧分压侧分别是空气或氧气,低氧分压侧是高纯氦气。研究表明,膜的厚度越薄,测试温度越高,透氧率就越大,1.0mm厚的膜在900℃时的透氧率为3.36×10^-7mol/cm²·s。 用稳态法也研究了La替代Y的Y_1-xLa_xBa₂Cu₃O_7-δ（x=0.1,0.3,0.5,0.8和1.0）、Ca替代Y的Y_1-yCa_yBa₂Cu₃O_7-δ（y=0.1,0.2,0.3和0.4）及简单研究了Co替代Cu、Fe替代Cu和一些双组分同时替代的致密透氧膜的透氧性能。实验发现,透氧速率随着La替代Y的比例x的增加而增加,LaBa₂Cu₃O_7-δ（x=1.0）膜的透氧率在950℃和1000℃分别达到0.92μmol/s·cm²,1.22 μmol/s·cm²;而Ca替代Y的最佳比例则是y=0.2～0.3,y=0.2、y=0.3厚1.0mm的样品透氧率J_O2在1000℃分别达到1.223μmol/s·cm²,1.207μmol/s·cm²。在测量过程中随着温度的升高,氧空穴的有序-无序转变导致透氧率有一个突然增加。Co替代Cu、Fe替代Cu的材料透氧性能相比YBCO并没有提高;双组分同时替代的也仅Y_0.7Ca_0.3BaSrCu₃O_7-δ的氧渗透性能得到提高,厚为1.66mm的膜在940℃时的透氧率达到了0.797μmol/s·cm²。 本文的研究工作为继续开展这方面的研究积累了丰富的实验技巧和实验数据。更多还原

【Abstract】 The conception, the category, the research evolvement, the oxygen permeation mechanics and theoretical calculation formula of oxygen permeation flux of mixed ionic and electronic conductivity membranes (MIECM) are firstly presented in this thesis. In addition, MIECM’s preparing methods, performance token, application and some problems in development are reviewed. The discovery, the character of structure, and some oxygen behavior of the high temperature superconductor material YBa2Cu3O7-δ (abbreviation, YBCO) are described too.We study the oxygen adsorption and desorption of YBCO under different temperatures in switching N2→O2→N2 atmosphere by transient thermogravimetry (TG) method, and estimate the oxygen adsorption and desorption rates. The results show that YBCO has strong oxygen permselectivity under the measure condition of transient TG, and the process of oxygen adsorption and desorption is reversible. The course of oxygen adsorption is rapid, oppositely, the course of oxygen desorption is slower. At the same time, the results show that oxygen adsorption or desorption is exterior diffusion only in beginning period, then body diffusion comes to act, further more, in the last balance period body diffusion is in the dominant status. The oxygen contents of the samples BaRE(Cu0.5Fe0.5)2O5+δ (RE=Lu~Pr) are studied by TG. The results show that only the oxygen stoichiometries of BaiRE(Cu0.5Fe0.5)2O5+δ (RE = Pr, Nd, Gd) vary with the variation of temperature or oxygen pressure. The surface oxygen reaction rate constants and the oxygen permeation fluxes of BaiRE(Cu0.5Fe0.5)2O5+δ (RE-Pr, Nd, Gd) are estimated by the transient thermogravimetric analysis method, which is lower than YBCO.The oxygen permeation rates at different temperature of YBCO membranes with different thickness are measured by steady state permeation method (gas chromatography analysis). The atmosphere at high oxygen partial side of the membranes is air or oxygen, but high purity helium at low oxygen partial side. The researches show that the thinner the membrane or the higher measuring temperature is, the higher the oxygen permeation rate. The oxygen permeation rate at 900℃ of YBCO membrane with thickness lmm is 3.36x10~-7mol/cm~2s.The oxygen permeation properties of Yi_xLaxBa2Cu3O7-5 (x = 0.1, 0.3, 0.5, 0.8 and 1.0) substituting La for Y and Y1.yCayBa2Cu3O7.5Cy = 0.1, 0.2, 0.3 and 0.4) substituting Ca for Y are also studied by the steady state method. The samples of substituting Co for Cu, substituting Fe for Cu and double elements substitution are also investigated simply. The oxygen permeation fluxes of Yi^La^BaaCusOy.,; membranes increase with the increase of La content. Jo of LaBa2Cu3O7.g (x=1.0) membranes with thickness 1.0mm reaches 0.92umol/s-cm2, 1.22umol/s-cm2 at 950°C, at 1000°C, respectively. While the optimum Ca substitution proportion is y = 0.2-0.3, and Jo of Yi^CayBaaCusO?^ reaches 1.223umol/s-cm2, 1.207 umol/s-cm2 at 1000°C, when ^=0.2, .y=0.3, respectively. There is an obvious increase in the measuring process with increasing temperature due to an order-disorder transition of the oxygen vacancies in the membrane material. The oxygen permeability of the materials of substituting Co for Cu or substituting Fe for Cu is not improved compared with YBCO. Only the oxygen permeability of Yo^CaojBaSrCusOy-g in double elements substitution materials is improved, and reaches 0.797umol/s-cm2 at 940°C with thickness 1.66mm.The investigation reported in this thesis has accumulated a lot of experimental technique and data for the following study on these subjects.更多还原