Electrochemical characterisation of 3Y-TZP–Fe2O3 composites

Abstract

The influence of the addition of ferric oxide to 3Y-TZP on the conductivity and microstructure of sintered Y-stabilised tetragonal zirconia ceramics (3Y-TZP) was investigated. A comparison was made between two different dense 3Y-TZP -aFe 2 O 3 composites. Compacts were made by pressureless sintering at 1150 jC or by sinterforging at 1000 jC and 100 MPa. The sinterforging process resulted in smaller zirconia and hematite grains and a higher monoclinic zirconia content as compared to the compact that was sintered pressureless. The high monoclinic content led to loss of ionic conductivity. The addition of ferric oxide caused electronic conductivity. The sinterforging resulted in a high concentration of metastable defects in the zirconiahematite composite, leading to a relatively high electronic conductivity. Heating above 380 jC caused irreversible loss of these defects and a large decrease in electronic conductivity. D

ZrO2-Supported Fe2O3 for Chemical-Looping-Based Hydrogen Production: Effect of pH on Its Structure and Performance As Probed by X-ray Absorption Spectroscopy and Electrical Conductivity Measurements

“…These observations can be explained by the incorporation of Fe 3+ cations in the zirconia structure, substituting Zr 4+ cations. It has been reported that the incorporation of Fe 3+ in the ZrO 2 lattice stabilizes the metastable t-ZrO 2 phase. ,− It should be noted that the mutual cationic solubility in the Fe–O–Zr system is very low, with an equilibrium solubility of Fe 2 O 3 in ZrO 2 of 2 mol % and ZrO 2 in Fe 2 O 3 of 1 mol % at 1373 K …”

Factors Governing Oxygen Reduction in Solid Oxide Fuel Cell Cathodes

“…Workers have generally shown that when YSZ is implanted or alloyed homogeneously with Fe or Mn, its electrical conductivity is not significantly enhanced, even under moderately reducing conditions. 82,243,[284][285][286] Second, in isotope studies of lowtemperature bifunctional CO oxidation catalysts, such as Au/Fe 2 O 3 , workers have shown that the role of the transition metal in the support is essentially catalytic, i.e., stabilization of physisorbed O 2 at the Au/oxide interface, leading to enhanced oxidation rates. [287][288][289] It is likewise possible that enhanced performance of metal cathodes on YSZ incorporating transition metals or (other d-orbital cations) is an electrochemical-kinetic effect localized to the TPB where by "localized" we mean simply "within a distance accessible by electrons from the electrode material".…”

“…First, it should be emphasized that a finite rate of oxygen exchange at the electrolyte surface (as measured at equilibrium by isotope methods) is a necessary but insufficient criterion for finite rates of oxygen reduction; for there to be a net production of O 2- at the electrolyte surface, electrons must also be able to gain access to the surface. Workers have generally shown that when YSZ is implanted or alloyed homogeneously with Fe or Mn, its electrical conductivity is not significantly enhanced, even under moderately reducing conditions. ,,− Second, in isotope studies of low-temperature bifunctional CO oxidation catalysts, such as Au/Fe 2 O 3 , workers have shown that the role of the transition metal in the support is essentially catalytic , i.e., stabilization of physisorbed O 2 at the Au/oxide interface, leading to enhanced oxidation rates. − It is likewise possible that enhanced performance of metal cathodes on YSZ incorporating transition metals or (other d-orbital cations) is an electrochemical−kinetic effect localized to the TPB where by “localized” we mean simply “within a distance accessible by electrons from the electrode material”. Indeed, as shown in Figure , the enhancements observed by van Hassel and co-workers upon implantation of Fe into YSZ correspond to an increase in the apparent exchange current density while the Tafel slope remains constant over several orders of magnitude.…”

Development of Fe2O3/YSZ ceramic plates for cryogenic operation of resistive-protected gaseous detectors

“…Under these conditions, the conductivity is predominantly ionic. When the content of Fe-based impurities exceeds the solubility limit at around 6% mol (2.84%wt), paths of hematite have been reported to generate across the sample (Verkerk et al, 1982;Kharton, 1999;Boukamp, 2003). Setup for the characterization of a cryogenic RP-WELL at 90 K (vapor pressure 1.2 bar).…”

“…In this case the dopant acts as an electron donor, up to concentrations of 10% Zr atoms per Fe atom (or 16.3%wt, in weight percentage), when a new phase is formed. For larger concentrations, ZrO 2 (zirconia) might be used instead, leading to speculation of additional contributions to Frontiers in Detector Science and Technology frontiersin.org the electron conductivity, either through the grain-boundary (Boukamp, 2003), or electron hopping through Fe cations in the zirconia lattice (Kharton, 1999). Given this landscape, a natural possibility was to evaluate ceramics based on Fe 2 O 3 and zirconia stabilized with yttria at 8% molar (hereafter yttria-stabilized zirconia, YSZ) for which a large body of experience exists ( (Verkerk et al, 1982;Slilaty, 1996;Gao et al, 2008;Molin et al, 2009;Bohnke et al, 2014;Guo, 2021) and references therein).…”