Highly sensitive impedance-based propene sensor using stabilized zirconia and zinc oxide sensing-electrode

Aimed at an environmental monitoring of hydrocarbons (HCs), a new-type impedancemetric sensor was fabricated by using an yttria-stabilized zirconia (YSZ) tube and ZnO sensing-electrode (SE). The fabricated tubular sensor was examined for detection of low concentrations of propene (C₃H₆) in the presence of 1.35 vol.% H₂O and 400 ppm CO₂ at 600 °C. As a result, it was found that the present sensor could detect the low concentrations of C₃H₆ in the range of 0.05–0.8 ppm and the sensitivity varied linearly with C₃H₆ concentration. In addition, the C₃H₆ sensitivity was almost invariant with the changes in the concentration of water vapor and the interferences to other gases, such as NO₂, NO, H₂, CO and CH₄, were insignificant.     

在RuO2|Pd|YSZ|PddeNOx电解池中O2-传导的速控步骤

研究了500～750℃富氧条件下RuO₂|M|YSZ|Pd(M=Ag,Pd,Pt,Au)固体电解质电解池在0～4V直流电压下对NO的分解性质.600℃下,O^2-在Pd|YSZ阴极界面处的传导是O^2-在RuO₂|Pd|YSZ|Pd固体电解质电解池中传导过程的速控步骤.反应温度越低,RuO₂|Pd|YSZ|Pd电解池上NO电催化分解相对于氧分解的选择性因子α越大.600℃下O^2-在M|YSZ阴极界面处的传导阻力按Ag2|Ag|YSZ|Pd电解池上分解率为15.3%,NO选择性因子达到13.4.     

锰酸镧和氧化钇稳定的氧化锆复合阴极的研究

用交流阻抗,强极化和电导测量等方法考察了一系列不同氧化钇稳定氧化锆(YSZ)含量的锶掺杂锰酸镧(LSM)复合阴极的电化学性能,发现随着掺入YSZ量的增大,阴极性能大幅度提高,当YSZ质量分数为40%时,电极性能最好,电化学极化电阻约为1.18Ω/cm².通过分析发现,YSZ的掺杂使电极反应过程的控制步骤发生了变化.同时发现,随着YSZ含量的增加,电极的接触电阻增大.以Pt为电流收集层和40%的YSZ+LSM的复合电极形成的二层电极可有效地消除接触电阻,进一步提高了复合电极的性能.在1223K极化电阻从1.18Ω/cm²下降到0.41Ω/cm².     

单一混合固态源PE-MOCVD法制备YSZ薄膜及其表征

采用等离子体增强的MOCVD技术,以均匀混合的金属β-二酮鳌合物固态源Y(DPM)₃和Zr(DPM)₄作为前驱物,在NiO/SDC多孔阳极和多孔-αAl₂O₃衬底上制备了氧化钇稳定的氧化锆(YSZ)薄膜.研究了两种衬底对成膜过程和膜的结构以及微结构的影响,讨论了源区输运机制及薄膜生长动力学.XPS分析结果表明,薄膜中Y和Zr元素的摩尔比低于原始混合源中的Y和Zr元素的摩尔比,当混合源中的Y和Zr元素的摩尔比约为0.35:1时,可以获得无定形态的8%YSZ薄膜,经高温焙烧转化为单一立方相,其晶粒大小约为100nm,薄膜的生长速率约为7nm/min.     

Ultraviolet excitation of rare-earth-doped YSZ crystals

Abstract

The optical properties of nominally pure and Er³⁺- or Pr³⁺ -doped yttria-stabilized zirconia single crystals were investigated under UV light excitation. In the excitation spectra of both types of doped crystals, a broad UV band is observed. Under excitation with light of different wavelengths inside this band, the luminescence features of the doped crystals are different. YSZ: Pr³⁺ samples exhibit the characteristic 4f → 4f emission of the Pr³⁺ ions. In YSZ: Er³⁺ crystals, both the Er³⁺ ion and the intrinsic luminescence are observed. Host to Er³⁺ ion radiative energy-transfer is also demonstrated. No dependence of the transfer process with the excitation wavelength was found. These results suggest that the UV band in Er³⁺ -doped crystals is associated with the lattice-dopant ion interaction rather than with the 4f5d interconfigurational band of the Er^3? ions.     

不同含钴阴极在YSZ薄膜电解质固体氧化物燃料电池中的性能

固体氧化物燃料电池阴极材料的阻抗对固体氧化物燃料电池的性能有较大影响.我们通过XRD、对称电池以及单电池性能测试等方法比较系统地研究了4种最为常用的含钴阴极材料直接用于钇稳定化氧化锆（YSZ）电解质薄膜与通过引入SDC夹层后用于YSZ电解质薄膜后的性能.我们发现,不同的含钴阴极材料与YSZ材料之间都不同程度地发生相反应,在应用于YSZ电解质薄膜上时,相反应大大降低了含钴阴极材料的性能,在使用了SDC夹层后,单电池的功率输出显著提高.     

Partial electronic conductivity and electrolytic domain of bilayer electrolyte Zr0.84Y0.16O1.92/Ce0.9Gd0.1O1.95

Partial electronic conductivity and total conductivity have been determined by Hebb-Wagner polarization method and a.c. impedance spectroscopy, respectively, on bilayer electrolyte Zr_0.84Y_0.16O_1.92(YSZ)/Ce_0.9Gd_0.1O_1.95(GDC) with thickness ratios 10^− 3/1 and 10^− 4/1 at 800°, 900° and 1000 °C, respectively. While their ionic conductivities remain close to that of GDC, the electronic conductivities are suppressed the more from that of GDC towards that of YSZ the higher the thickness ratio, as expected. Even when the GDC-side is exposed to reducing atmosphere, the electronic conductivity is also suppressed, but to a less extent. It is suggested that oxygen activity distribution is discontinuous across the YSZ/GDC interface under ion-blocking condition, refuting the “continuity hypothesis” that has been usually adopted in calculating the oxygen activity distribution across a multilayer of mixed conductor oxides. The electrolytic domain widths of the bilayer electrolyte are reported depending on temperature, thickness ratio and direction of oxygen activity gradient imposed.     

Gas diffusion hindrances on Ni cermet anode in contact with Zr<Subscript>0.84</Subscript>Y<Subscript>0.16</Subscript>O<Subscript>1.92</Subscript> solid electrolyte

The electrochemical behavior of Ni cermet electrode with CeO_{2 ? x} additive in contact with YSZ electrode was studied by means of impedance spectroscopy in H₂, H₂O, CO₂, CO, He, and Ar gas media of various composition within the temperature range of 700 to 950°C. Near the equilibrium potential, the electrochemical impedance spectra of the studied electrodes indicate to three stages of electrode reaction. The polarization conductivity of the low-frequency stage of electrode reaction (σ_lf) is characterized with the following regularities: (a) temperature dependence of σ_lf has a positive slope in Arrhenius coordinates; (b) σ_lf increases upon replacement of gas mixture with lower mutual diffusion coefficient by mixture with higher mutual diffusion coefficient, while polarization conductivity values of other stages remain practically invariable; (c) concentration relationships of 1/σ_lfrecorded for constant activity of oxygen in the gas phase are linear in the 1/σ_lf vs. 1/P _{CO 2} (P _CO) coordinates; (d) no low-frequency stage of the electrode reaction is observed upon electrochemical inflow (outflow) of the gas reagents (reaction products) to (from) the test electrodes (current passing through closely pressed specimens and central specimen impedance measurement); and (e) no change in the gas flow rate affects σ_lf value. The observed regularities were explained by assuming the gas diffusion nature of the low-frequency stage of the electrode reaction. The gas diffusion layer thickness was estimated.     

Nano-structures in YSZ(1 0 0) surfaces: Implications for metal deposition experiments

The surface morphology of yttria stabilized zirconia (YSZ)(1 0 0) single crystals are examined by AFM and XPS before and after thermal annealing in air to 1000 °C. The surfaces show a large variability in topography which can be categorized in three types: (1) surfaces with well defined terraces, (2) surfaces with etch pits and no visible terraces, (3) surfaces with large square or rectangular holes with flat bottoms. All three types of surfaces show a large number of defects (pits, adatoms, steps) originating from the manufacturing process, and certain samples show large nano-structured arrays of self-organized lines at step edges. The evolution of the surfaces with time at 1000 °C and with higher temperatures was studied. Terraces are ultimately obtained for all sample types at 1300 °C, but the terrace shape is affected by the original defect structure. This history dependence is attributed to defect interactions modifying the annealing process. This is true even for UHV samples prepared using sputter-anneal cycles. The surface type is found to affect the nucleation, growth and sintering behaviour of palladium deposited by electron beam evaporation. For type 3 samples the metal nucleates at step edges outside the holes to particles 6 Å in height, following heating to 135 °C the particles move inside the holes forming agglomerates up to 20 Å.     

T1系超导薄膜金属涂层的生长与特性研究

我们研究了T1-2212超导薄膜在带有YSZ／CeO2缓冲层和带有Ce02／YSZ／CeO2缓冲层的Ni金属RABiTS基带上的生长情况．基带上的缓冲层是采用PLD方法制备的，T1-2212薄膜的制备采用了磁控溅射和后热处理两步方法．XRD实验结果表明。T1-2212薄膜都具有很好的C轴垂直于膜面的织构，并具有双向外延生长特性．在CeO2／YSZ／CeO2／Ni基带上制作的T1-2212薄膜的Tc达到102．8K，J,（77K,0T）达到2.6MA／cm^2；在YSZ／CeO2／Ni基带上薄膜Tc可达97．7K，Jc（77K,0T）也可以达到0．45MA／cm^2.