Materials Research Society

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Research into the growth of high-quality single crystal thin films of high transition temperature {Tc} superconductors have stimulated interest in other perovskite metal oxides with a variety of physical properties. Thin films of perovskite materials are among the major focal research areas for optical, sensor, electronic, and superconducting applications. Two lanthanum-based oxygen/electronic conducting perovskite oxides of particular interest for high temperature fuel cell electrodes and interconnects and for other electrochemical applications such as oxygen separation devices are La{sub 1{minus}x}Sr{sub x}MnO{sub 3{minus}y} and La{sub 1{minus}x}Sr{sub x}CoO{sub 3{minus}y}. The La-based perovskites are valuable for these technologies because they reduce interfacial resistances by eliminating the need for a three phase contact area (gas, metal electrode, electrolyte). In addition, these oxides may also serve a valuable role as novel catalysts or catalytic supports; however, little is known about what catalytic properties they may possess. Fundamental study of the electrochemical, diffusional oxygen transport, and surface catalytic properties of these materials can be greatly simplified if the complications associated with the presence of grain boundaries and multiple crystallite orientations can be avoided. Therefore, single crystals of these La-based perovskites become highly desirable. In this work, the authors report the structural and electrical properties of highly oriented thin films of La{sub 0.84}Sr{sub 0.16}MnO{sub 3} and La{sub 0.8}Sr{sub 0.2}CoO{sub 3} grown on single crystal Y-ZrO{sub 2} substrates. An addition, the authors have demonstrated growing, in situ, epitaxial multilayer perovskite/fluorite/perovskite configurations for fundamental fuel cell modeling.

The ultimate bearing capacity of rigid piles and pile groups in sand has been determined under various combinations of eccentricity and inclination of the load varying from the vertical to horizontal directions. The results of load tests on single model piles and free‐standing groups are compared with theoretical estimates. The influence of eccentricity and inclination of the load on the bearing capacity can be represented by simple interaction relationships between the ultimate loads and moments and between the axial and normal components of the ultimate load. The effect of a pile cap resting on the soil in piled foundations is examined on the basis of previous theory and model test results.