Bismuth ruthenate

There is a need to develop new types of oxide electrodes for reactions of technological importance with emphasis on both high electrocatalytic activity and stability. For example, pyrochlore-type oxides, e.g. lead or bismuth ruthenates, have shown excellent catalytic activity for the oxygen evolution and reduction reactions and should be further investigated to elucidate the reasons for such high activity. The long term stability of such ruthenate electrodes is questionable, however. 

The reactants used were the more soluble cation sources, generally the nitrates. The aqueous solutions of these cation sources were combined in a post transition metal to noble metal ratio appropriate for the ultimately desired pyrochlore stoichiometry. For lead ruthenate syntheses the reactant Pb Ru ratio was required to be slightly higher than the intended final Pb Ru ratio because of the high solubility of lead relative to ruthenium. For bismuth ruthenate syntheses the Bi Ru ratio was required to be slightly lower than the intended final Bi Ru ratio because of the higher solubility of ruthenium. 

In the case of the Bi2[Ru2-x x]07-y series, it is possible to explain the bismuth substituted pyrochlore either as resulting from the substitution of ruthenium by Bi ", with subsequent vacancy formation on the anion lattice, or by substitution of ruthenium by pairs of Bi and Bi5+, with no anion vacancy formation necessary. Any of the above valence distributions for the bismuth ruthenates could account for the expanded lattice parameter since they all involve average B-site ionic radii larger than Ru ". ... 

Synthesis of the bismuth-substituted bismuth ruthenates is, in most respects, similar to that of the lead ruthenate series. Precipitation/crystallization is effected in a relatively oxidizing. 

While the oxygen electrocatalysis results reported here have been those obtained specifically on the lead ruthenate series, essentially equivalent results were obtained on the bismuth ruthenate series. 

The functional phase in thick-film resistors is a mixture of electrically conducting (or semiconducting) ceramic powders such as ruthenium dioxide (RUO2), bismuth ruthenate (Bi2Ru207), lead ruthenate (Pb2Ru206), and Ag-Pd-PdO mixtures for use in air-fired pastes and tantalum nitride (TaN) for nitrogen-fired pastes. The resistance of thick-film resistors is specified in terms of sheet resistance, which has units of ohms/square (Q/D). 

The active phase for resistor formulation is the most complex of all thick-film formulations due to the large number of electrical and performance characteristics required. The most common active material used in air-fireable resistor systems is ruthenium, which can appear as RUO2 (ruthenium dioxide) or as BiRu207 (bismuth ruthenate). 

Ryll T, Bruimer A, Ellenbroeck S, Bieberle-Huetter A, Rupp JEM, Gauckler LJ (2010) Crystallization and electrical conductivity of amorphous bismuth ruthenate thin films deposited by spray pyrolysis. Phys Chem Chem Phys 12 13933... 

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