The perovskite ceramic BaCe0.2Zr0.7Y0.1O3‐δ (BCZY27) with a small addition of NiO has previously been shown to densify at a reasonable sintering temperature while maintaining high protonic conductivity. However, some questions remain regarding the role, location, and resulting phase of the NiO addition. Transmission electron microscopy and atom probe tomography (APT) were used to analyze BCZY27 specimens before and after use as a hydrogen separation membrane. The effects of electrolyte operation on the local chemistry were explored. Grain boundaries were specifically targeted due to their higher energies and importance for overall conductivity. The compositions measured by APT were found to be dependent on the laser energy used for analysis, but conditions were found which gave results reasonably consistent with x‐ray fluorescence results. Specimens before and after electrolytic use showed no measureable difference in the local chemistry. Most grain boundaries exhibited little compositional variation from the bulk material, with only a slight increase in yttrium being apparent. A few grain boundaries had particles 2–15 nm in diameter, which were found by APT to be NiO.

The influence of NiO on the stabilization and microstructure of yittria (Y2O3)‐stabilized zirconia (ZrO2) (YSZ) is examined. Cold‐pressed powders comprising varying amounts of NiO, 8 mol%Y2O3, and ZrO2 were sintered at 1500°C for 4 h. Specimens were subsequently given a 100 h heat treatment at 1500°C. Phase analysis by X‐ray diffraction revealed that the presence of NiO leads to a greater amount of cubic phase ZrO2 for the sintered specimens compared with the control specimens. The cubic ZrO2 lattice parameter was significantly smaller for specimens containing NiO, revealing that Ni2+ ions likely enter the cubic ZrO2 lattice and play a role in decreasing the time and temperature required for stabilization of the cubic phase. A spherical diffusion model was used to estimate the diffusion of Y3+ and Ni2+ into ZrO2. These results are discussed in the context of the role of NiO in the synthesis of YSZ.

Fabrication of defect free co-sintered electrolytes with thickness between 12 μm and 40μm has been demonstrated on planar and tubular cells produced via a spray coating process. Leak testing using a helium leak method showed low diffusional leak rates for cells using optimized spray parameters. The electrolytes were characterized using scanning electron microscopy to qualitatively assess pin holes. Average open circuit voltages (OCVs) of 1080 mV were obtained on tubular cells with spray-coated electrolytes using 3% humidified hydrogen as the fuel. This paper presents spray coating as a viable, cost effective method for electrolyte application in co-fired, anode supported SOFCs.

Manufacturing cost remains one of the major issues facing the solid oxide fuel cell (SOFC) industry. In the anode supported SOFC design, the cermet anode constitutes around 90% of the total material required to build a cell, making the technology very sensitive to anode raw material price. A new patent-pending process called “nickel yttria reaction-sintered zirconia (NiYRSZ)” has been developed for manufacturing SOFC anodes at a fraction of the cost. Typically, the solid component of the anode consists of about 50/50 volume percent nickel and 8 mole percent yttria stabilized zirconia, the latter being a rather costly material. It was discovered that zirconia and yttria powders sintered in the presence of nickel oxide readily form the cubic phase at moderate temperature. Cells manufactured using this process show excellent microstructures for anode supports: a strong bond between the electrolyte and the anode, and a high porosity without addition of pore formers. The strength of the anode was 100 MPa making the material equivalent or slightly superior to an anode fabricated with the traditional NiO/8YSZ material of similar porosity. The resistivity of the material was measured at 850°C and found to be less than 2 mΩ·cm. Cell performance was also compared to cells manufactured with traditional material. Every indication is that SOFC anodes fabricated with this new method perform as well as anodes made with the conventional material set.

For more than three decades, perovskite materials based on doped barium/strontium cerate/zirconate have been studied as potential hydrogen separation membranes and electrolyte for proton ceramic fuel cells or electrolysis cells.  It is well known that cerates are unstable in carbon dioxide and high steam containing atmospheres. Additionally, higher conductivities are obtained with barium instead of strontium on the A-site of the perovskite. Therefore, devices are designed using solid solution of barium cerate-zirconate with low amount of cerium (BaCexZr0.9-xY0.1O3-δ, BCZY). The protonic defects (OHo ·) are incorporated in the material by the hydration equation, also known as the Wagner equation [1] (Eq. 1), in which water dissociates in oxygen vacancies. H2O (g) + Vo ··  + Oo x ↔ 2 OHo ·  (1) The incorporation and removal of protonic defects create chemical expansion and contraction respectively, which have a tremendous impact on the mechanical strength of the device: the difference of coefficient of thermal expansion (CTE) between the electrolyte and the electrodes increases in the hydration/dehydration region and can cause failure of the device, especially as the trend is to decrease the electrolyte thickness. Therefore, it is imperative that the dehydration temperature and chemical expansion is considered for sealing, startup, and operation of devices based on proton-conducting ceramics. There is limited high temperature X-ray diffraction (HT-XRD) work on BaCexZr0.9-xY0.1O3-δ materials. Hiraiwa et al.  [2] studied the chemical expansion/contraction of BaZr0.8Y0.2O3-δ (BZY20) in dry oxidizing atmosphere and reported the presence of chemical expansion in the temperature range of 300-450 °C, due to the dehydration of the sample (water incorporated during fabrication) and also found that the chemical expansion depends on the high temperature thermal history of the part.  Andersson et al. [3] recorded HT-XRD on hydrated BZY in flowing synthetic air (1 ppm H2O) and determined a dehydration temperature of about 300 °C. In this work, HT-XRD was used to determine the thermal and chemical expansion of BZY10 (BaZr0.9Y0.1O3-δ) and BCZY27 (BaCe0.2Zr0.7Y0.1O3-δ). Two sets of experiments will be presented and the pros and cons of each will be detailed: in-situ hydration and pre-hydration via autoclave. Figure 1 displays the lattice parameter of BCZY27 recorded while cooling in dry 4% H2 and 4% H2 containing 1 or 3% moisture. The knee in the curve observed in the temperature range 300-500°C in moist conditions is related to hydration of the material. The lower CTE in this temperature range comes from the competition between the contraction due to cooling and the expansion due to protonic defect incorporation. Additionally, an ideal start-up procedure for BCZY based materials will be proposed. [1] V.S. Stotz, C. Wagner, Ber Bunsenges Phys. Chem. 70 (1967) 781 [2] C. Hiraiwa, D. Han, A. Kuramitsu, A. Kuwabara, H. Takeuchi, M. Majima, T. Uda, J. Am. Ceram. Soc. 96 (2013) 879 [3] A.K.E. Andersson, S.M. Selbach, C.S. Knee, T. Grande, J. Am. Ceram. Soc. 97 (2014) 2654 Figure 1