[en] The oxidation/reduction properties of various bismuth molybdates, molybdenum trioxide, bismuth oxide, uranium antimonate, and iron antimonate have been studied in an effort to correlate them to their catalytic properties. The temperature at which γ-phase bismuth molybdate is prereduced plays an important role in the behavior the catalyst exhibits under reoxidation conditions. The overall behavior of γ-phase bismuth molybdate under catalytic conditions may be divided into two temperature regimes: below 360⁰C the catalyst shows a higher rate of propylene adsorption than product desorption, and above 360⁰C where produced desorption is dominant. This temperature is the same at which the Arrhenius plot for the reaction has a break. Several reduction of γ-bismuth molybdate results in the formation of clusters of bismuth metal and crystallites of molybdenum dioxide. This is irreversible. The reoxidation of the bismuth molybdate catalysts shows the presence of two oxygen incorporation temperatures. The ratios of the areas under these peaks are not the same for the three catalysts. Uranium antimonate shows a lesser degree of lattice oxygen participation. During several reduction the catalyst decomposes partially and an excess of antimony is evident. The isothermal reduction profiles of the catalysts permitted their classification into either of two reduction models: (A) α-, β-, γ-phase bismuth molybdates, molybdenum trioxide, bismuth oxide, and the equimolar mixture follow the nucleation model, (B) uranium antimonate, and iron antimonate following the shrinking sphere model. These models have been correlated to certain characteristics of these catalysts. Group A catalysts show a high degree of lattice oxygen participation (migration of bulk oxygen to surface nuclei). In contrast in group B catalysts only a few layers of oxygen are peeled off during catalysis

[en] This patent describes a process of forming on a substrate a uniform metal oxide coating which exhibits a superconducting transition temperature in excess of 90 degrees K. containing a conductive oxide crystallization phase which satisfies the formula: P₂A_3-xA'_xC₂ where P is bismuth optionally in combination with less 10 mole percent antimony, A is strontium, A' is calcium, C is copper, and x is 0.5 to 1.5. It comprises: applying to a surface of the temperature with a perovskite crystal structure or an alkaline earth oxide a coating of a solution consisting essentially of a volatilizable film solvent, metal-ligand compounds of each of P,A, and A' containing at least one thermally volatilizable organic ligand, and at least one copper-ligand compound containing a thermally volatilizable carboxylic ligand, the ligands each containing less than 30 carbon atoms, removing the solvent and ligands from the substrate by heating in the presence of oxygen to form a heavy pnictide mixed alkaline earth copper oxide coating of 1.5 μm or less in thickness on the substrate, and forming the crystalline conductive coating on the substrate by heating the oxide coating to its crystalline temperature followed by cooling in the presence of oxygen

[en] This patent describes an article comprised of a substrate and an electrically conductive layer located on the substrate characterized in that the electrically conductive layer is comprised of greater than 45 percent by volume of a crystalline rare earth alkaline earth copper oxide exhibiting a ratio of metals satisfying (Ia) or (IIa) effecting crystal growth by heating in the temperature range of from 975 degrees to 1059 degrees c., and cooling the coating in the presence of oxygen at a rate of less than 25 degrees C per minute until it reaches a temperature of from 550 degrees to 450 degrees C

[en] This patent describes a process of preparing an article comprised of a substrate and a crystalline electrically conductive rare earth alkaline earth cooper oxide coating on the substrate exhibiting a T_c in excess of 30 degrees K. It comprises: choosing the substrate from the class consisting of strontium titanate, magnesia, and alumina; applying to the substrate a coating of a solution. The solution consisting essentially of a volatilizable film forming solvent, metal-ligand compounds of each of rare earth and alkaline earth containing at least one thermally volatilizable organic ligand, and at least one cooper-ligand compound containing a thermally volatilizable carboxylate ligand; removing the solvent and organic ligands from the substrate by heating in the presence of oxygen to form a coating of less than 1μm in thickness; and forming a crystalline conductive metal oxide coating on the substrate by heating to a temperature in the range of from 900 degrees to 1100 degrees C followed by contract with air or an oxygen enriched atmosphere during cooling

[en] In this paper, the authors demonstrate the homoepitaxial growth of SrTiO₃ prepared by the method of metallo-organic decomposition (MOD). Thin films of SrTiO₃ are prepared by spin-coating and thermal decomposition of a solution of metallo-organic compounds, on single crystal, left-angle 100 right-angle oriented, SrTiO₃ substrates and subsequently heat treated at temperatures ranging from 650 degrees C to 1100 degrees C for 30 minutes. Heat treatment at 1100 degrees C results in the formation of single-crystal SrTiO₃, perfectly aligned with respect to the underlying substrate. Ion-channeling analysis shows that the transformation to single-crystal material proceeds epitaxially from the coating-substrate interface towards the surface of the sample. Transmission electron microscopy (TEM) studies of partially regrown samples reveal two distinct phases: an epitaxially aligned single-crystal phase, adjacent to the substrate, and a polycrystalline phase on top

[en] Interactions between superconducting Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8+//sub x/ films and substrates were investigated by ion backscattering, x-ray diffraction, and four-point probe resistivity measurements. During annealing at temperatures above- 800 /sup 0/C, Bi/sub 2/Sr/sub 2/CaCu/sub 2/ oxide films rapidly reacted with alumina, Si, Si covered with SiO/sub 2/, and quartz, resulting in catastrophic failure. Zr-based barrier layers were used to minimize film-substrate interactions. When a single ZrO/sub 2/ layer was interposed between the superconducting oxide film and the underlying substrate, the Bi/sub 2/Sr/sub 2/CaCu/sub 2/ oxide films showed a large-grained polycrystalline microstructure and exhibited the orthorhombic structure. Films on sapphire showed transitions to the superconducting state beginning near 100 K with zero resistance achieved at 70 K. Films on Si and thermally grown SiO/sub 2/ showed a similar drop in resistance around 95 K, whereas the transition was broad and the zero resistance state was not reached. For films on quartz, high thermal stress caused cracking of the superconducting oxide film. Best results were achieved using a barrier composed of a Zr-Si-O mixed layer underneath ZrO/sub 2/. In this case, the films grown on Si and quartz were uniform and showed the onset to superconductivity at 95 K, attaining zero resistance at 70 K