Researchers from the University of Michigan, including Ximeng Wang, Yongfeng Zhang, Dmitry Skachkov, Arnab Das, Junliang Liu, Alexander Kvit, Jennifer T. Choy, and Adrien Couet, have published a study in the Journal of Physical Chemistry C that sheds light on the charge redistribution at metal-zirconia interfaces. This research could have significant implications for the energy industry, particularly in the design and optimization of high-temperature oxidation-resistant materials.
The study focuses on nanoscale metallic inclusions (NMIs) found within oxide scales formed during high-temperature oxidation. These NMIs challenge conventional corrosion theories that assume homogeneous, fully oxidized films. The researchers used tetragonal zirconia (tZrO2) facing a series of face-centered cubic (fcc) metals as a model system to investigate both short-range and long-range charge redistributions across metal-oxide interfaces.
Using density functional theory (DFT) calculations coupled with continuum modeling, the researchers found that metal-oxide contact induces a short-range charge redistribution confined to a few atomic layers. This short-range redistribution is dominated by metal induced gap states (MIGS) in tZrO2 facing noble metals like gold and silver, and by chemical bonding in tZrO2 facing active metals like aluminum. The study also revealed a long-range redistribution of space charge that can extend over macroscopic distances within weakly doped oxides.
The researchers’ continuum theoretical analysis, informed by DFT calculations, showed that the range of space-charge redistribution is governed by the doping level of tZrO2. Additionally, the Schottky barrier height (SBH) exhibits a stronger dependence on the metal work function than the doping level. Both the short-range and long-range charge redistributions can alter the transport of charge carriers via their associated electric fields, extending several nanometers to hundreds of nanometers from the interface, depending on the doping concentrations.
This research suggests that NMIs can cause heterogeneous oxide growth, which could have practical applications in the energy sector. For instance, understanding and controlling charge redistribution at metal-oxide interfaces could lead to the development of more durable and efficient high-temperature materials for energy generation and conversion technologies. This could include applications in nuclear reactors, gas turbines, and other high-temperature industrial processes.
Source: Wang, X., Zhang, Y., Skachkov, D., Das, A., Liu, J., Kvit, A., Choy, J. T., & Couet, A. (2023). Charge redistribution at metal-ZrO2 interfaces: A combined DFT and continuum electrostatic study. Journal of Physical Chemistry C.
This article is based on research available at arXiv.