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Electrical conductivity of Sr2-xVMoO6-y (x = 0.0, 0.1, 0.2) double perovskites has been investigated in a reducing atmosphere at temperatures up to 800 °C. This material has a key application in solid oxide fuel cell anodes as a mixed ion and electron conductor. A solid state synthesis technique was used to fabricate materials and crystal structure was verified through x-ray diffraction. Subsequent to conventional sintering in a reducing environment, elemental valence states were indentified through x-ray photoemission spectroscopy on the double perovskite material before and after annealing in a hydrogen environment. Samples exhibited metallic like conduction with electrical conductivities of 1250 S/cm (Sr2VMoO6-y′), 2530 S/cm (Sr1.8VMoO6-y″), and 3610 S/cm (Sr1.9VMoO6-y‴) at 800 °C in 5% H2/95% N2, with a substantial increase in conductivity upon cooling to room temperature. Room temperature electrical conductivity values for Sr1.9VMoO6-y‴ make it a candidate as the highest electrically conductive oxide known. Highly insulating secondary surface phases, Sr3V2O8, and SrMoO4, begin to reduce at 400 °C in a hydrogen environment, as confirmed by X-ray photoemission and thermal gravimetric analysis. This reduction, from V5+ and Mo6+ to lower valence states, leads to a large increase in sample electrical conductivity.

Ferritic stainless steel (FSS) bipolar plates are widely used to interconnect individual cells in planar Solid Oxide Fuel Cell (SOFC) stacks. In this study, thin films of ceramic and cermet electrode materials, La 0.8 Sr 0.2 MnO 3 (LSM) for the cathode and Ni-Y 2 O 3 /ZrO 2 (Ni-YSZ) for the anode, were screen printed on Sanvik's Sanergy HT, a specialty FSS alloy (with and without Co or Co/Ce surface coatings). Samples were then placed in a test rig which allows simultaneous exposures to humidified (3% H 2 O) single (air/air) and dual atmospheres (air/H 2 ) at 800 • C for 100 hours. This research is focused on the FSS surface oxide layers and the phenomena governing materials interactions during realistic SOFC exposures that drive degradation. The surface oxide layer composition and morphology are heavily influenced by the dual atmosphere exposures and contact with electrode materials. For example, air-side surface oxide layers are generally thicker and contain more Fe than those formed in single-atmospheres, and surface oxide layer thickness and composition is altered in the presence of contacting electrodes in comparison with gas-only exposures. These and other recent data suggest that corrosion studies performed without relevant SOFC stack environments (e.g., air-only and without contacting electrodes) may not reveal all of the pertinent high-temperature behaviors.

The entirely accidental observation of increased sintering performance of nickel-infiltrated yttria-stabilized zirconia (8YSZ) in a molybdenum and oxygen rich atmosphere was explored. Molybdenum and nickel were found to be synergistic sintering aids for 8YSZ. However, sintering had to take place in an atmosphere of flowing oxygen. Samples sintered in air consistently burst. The sintering performance, microstructure, and crystal structure of 8YSZ with additions of both Mo and Ni together are compared to the sintering performance, microstructure, and crystal structure of pure 8YSZ, 8YSZ with only Ni added as a sintering aid, and 8YSZ with only Mo added as a sintering aid. Enhanced densification and grain growth is observed in the Mo–Ni 8YSZ samples when compared to all other sintering samples. Order of magnitude sintering rate increases are observed in the Mo–Ni 8YSZ over that of pure 8YSZ. With a maximum sintering temperature of 1200 °C and a one-hour dwell, sintered densities of 85% theoretical density (5.02 g⁄cm3) are achieved with the Mo–Ni samples: a 57% increase in density over pure 8YSZ sintered with the same sintering profile. EIS results suggest conductivity may not be negatively impacted by the use of these two sintering aids at temperatures above 750 °C. Finally, the spontaneous generation of nickel-molybdenum nano-rods was observed on the 5, and 10 mol.% Mo–Ni infiltrated 8YSZ samples after being left under vacuum in a scanning electron microscope chamber, suggesting evaporation of a possible nickel–molybdenum compound from the sample fracture surfaces.