Connecting innovative sintering approaches for protonic ceramics to defect chemistry

• Applicant: Dr. Rotraut Merkle
• Subject Area: Synthesis and Properties of Functional Materials ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 556363981

This proposal is part of the research unit "Synergistic Design of Proton-Conducting Ceramics for Energy Technology". This research unit strives to improve proton conducting ceramics for ceramic fuel and electrolysis cells harnessing synergies between experiments (innovative sintering methods, multimodal characterization) and modelling (multi-scale modeling from atomistic calculations up to large-scale phase field models). The research unit will strongly use data-science tools (compiling extended data bases and exploiting them with machine learning tools) to optimize the materials and processing conditions. Sintering is a major bottleneck for BaZrO3-based proton conducting ceramics, because they require very high sintering temperatures, show slow densification and grain growth, and typically exhibit grain boundaries with decreased conductivity (in particular if problems such as BaO loss or secondary phase formation occur). Within the research unit, the present proposal strives to elucidate the complex relations between sintering processes, in particular novel approaches such as "ultrafast high-temperature sintering" UHS and "photonic sintering" PS, resulting ceramics microstructure, and the concentration and mobility of the relevant point defects (protons, oxygen vacancies) in the grain interior and at grain boundaries. One main topic is the investigation of the composition and properties of the liquid phase forming from NiO added as sintering aid, the resulting sintering mechanism, and the effects of this transient phase on the grain interior and grain boundary properties. The other main topic are the effects of the novel UHS, PS sintering processes on the materials properties. These processes are expected to modify the distribution of dopants and cation defects, and potentially also the structure of the grain boundary cores. This will affect the bulk proton uptake (hydration thermodynamics) as well as the bulk and grain boundary transport properties (space charge situation) which are both intensively investigated in the present proposal. Samples will be exchanged with other partners of the research unit to benefit from complementary sintering tools and characterization methods. The present project supplies experimental results to the simulation projects as input and validation data, and contributes to the joint processing-defects-micro-structure-property database. It will receive results from atomistic and large-scale simulations that assist in the interpretation of measured results, and obtain feedback for materials optimization from the exploitation of the joint database.

• DFG Programme: Research Units
• Subproject of: FOR 5966: Synergistic Design of Proton Conducting Ceramics for Energy Technology (SynDiPET)