Atomistic studies of grain boundary evolution during cold sintering of proton conducting oxides

• Applicants: Professor Dr.-Ing. Olivier Guillon; Professor Dr. Joachim Mayer
• Subject Area: Glass, Ceramics and Derived Composites ; Synthesis and Properties of Functional Materials
• Term: from 2021 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 455434186

The Cold Sintering Process was only discovered in 2016 and is now widely promoted as the new paradigm shift for low temperature (<300°C) processing of ceramics and composites. The process relies on high-pressures (up to 600 MPa, much larger than in standard hot pressing) and the addition of a liquid phase such as pure water or aqueous solutions with dissolved precursors of the solid phase. Such ultra-low temperature densification methods have a large potential not only to develop novel ultrafine-grain microstructures, but also to reduce the carbon footprint and high energy consumption connected with the conventional firing of ceramic materials.In our project, we aim at a fundamental understanding of the underlying mechanisms down to the atomistic scale in order to establish reliable processing routines and the basis for tuning of properties of high performance ceramics by cold sintering. We therefore implement novel high-resolution transmission electron microscopy (HRTEM) techniques with which each stage of the process, including the liquid state of the sintering additives, can be analyzed. Our results are key to understand, control and establish cold sintering as promising alternative to high temperature sintering. As a model material, proton conducting barium cerate-zirconate was selected as test case to prove our research hypothesis and to optimize a technological system. Our goal is a fundamental understanding of the mechanisms controlling cold sintering of the barium cerate-zirconate (BCZ) perovskite, and how this processing method influences its resulting electrochemical properties. In general, BCZ offers a bright perspective as proton conductor and can be applied e.g. in proton conducting fuel cells, gas separation membranes and membrane reactors to recover hydrogen from exhaust gases using waste heat from industrial processes.

• DFG Programme: Research Grants