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Vanadium oxide thin films were deposited using pulsed direct current (dc) magnetron sputtering in an atmosphere containing argon and oxygen. The total pressure was varied from 2.5 to 15 mTorr, and the oxygen-to-argon ratio was varied from 2.5 to 30%. The resulting films were characterized using Rutherford backscattering spectroscopy (RBS), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS), and glancing incidence x-ray diffraction (GIXRD). Electrical resistivity was calculated from I–V curves acquired from two-point-probe measurements and thicknesses measured from bright-field TEM images of cross-sectioned samples. TEM and GIXRD were used to characterize the crystallinity of each film. A transition from nanocrystalline to amorphous growth was observed with increasing partial pressure of oxygen. In all samples, the only crystalline phase observed was cubic vanadium oxide with the sodium chloride structure. Though the cubic VOx equilibrium phase field is limited to a maximum of x = 1.3, the cubic phase was observed with a value of x up to 2 in the present work. It was apparent from electron diffraction data that increased oxygen content correlated with an increase in the film disorder. The increase in oxygen content also corresponded with an increase in the film resistivity, which varied over 7 orders of magnitude from 1.18 × 10−3 to 2.98 × 104 Ω·cm. The temperature coefficient of resistance was found to increase with increasing oxygen content from −0.1 to −3.5%/°C. A direct correlation between film disorder and temperature coefficient of resistivity (TCR) was observed and could be exploited to engineer materials with the desired TCR.

The present study compares the feasibility of controlling the properties of a glass composite seal by adding nano‐ or micron‐scale yttria‐stabilized zirconia (YSZ) powders to a borate glass used for sealing electrolyte‐supported solid oxide fuel cells (SOFCs). The crystallization of the glass composites was found to be independent of the volume fraction of added YSZ, for both sizes of the additive. The variation of the flow properties of both composite seals was measured using a wettability test, and an increase of the contact angle was observed when the volume fraction of additives was increased. The major factor found to decrease spreading of the glass composite was the additive particle size, where shape retention was observed for the nanometer (nm)‐YSZ composites while spreading of the micrometer (μm)‐YSZ composites was observed under the same testing conditions. Examination of the microstructure showed that initially the Ba‐containing glass reacted with YSZ to form a BaZrO3 compound. Long‐time exposure at 800°C caused a large reduction in the coefficient of thermal expansion (CTE), which can be explained by increased formation of BaZrO3 and further change in glass composition. This change in CTE occurs rapidly for the nm‐YSZ composites, which is not observed for the μm‐YSZ composites. However, the adverse reactions occurring between the additives and the glass matrix were found to reduce the CTE of the glass composites to a value lower than the recommended limit for a system used for sealing SOFCs.