Yba <sub> 2 </ Sub> Cu <sub> 3 </ Sub> O <sub> 7-d </ Sub> And Elements Of Alternative Materials, Oxygen Permeability Study

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 N2â†'O2â†'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.