Kerstin NeuhausNov 24, 2023

Our new project on near-room T proton conductivity in pyrochlore-based materials has started this Nov, so I would like to talk about some points, which are the core of the project: crystalline proton conductors and Hebb-Wagner-type measurements🧵.

#SciComm #WomenInSTEM #battery 🧪👩‍🔬

Show threadKerstin NeuhausNov 24, 2023
Before we have a look specifically at pyrochlore materials, we have to delve a bit into transport mechanisms: most oxides that show proton conductivity also have a considerable oxygen ion conductivity at elevated temperatures and very often, those two are somehow coupled. Normally, transport in oxygen ion conductors occurs via a hopping process from oxygen vacancy to oxygen vacancy, but obviously there are no special proton vacancies in our materials.
Show threadKerstin Neuhaus
So there are two possibilities for the proton to move: either, it bonds on an oxygen ion and piggybacks through the structure (vehicle mechanism) or it bonds to an oxygen atom which then re-orients itself and the proton hops to the next oxygen atom in the structure (Grotthuss mechanism).
Nov 24, 2023 at 9:22amWeb
Show threadKerstin NeuhausNov 24, 2023

Let's now come to the pyrochlores: our benchmark material La2Ce2O7 shows a pyrochlore structure, which is a relative of the #fluorite and bixbyite structure. The mineral pyrochlore is relatively common with an ideal composition of Ca2Nb2O7.

📷: Brown pyrochlore crystal, Rob Lavinsky, iRocks.com

Show threadKerstin NeuhausNov 24, 2023
Big part of the research regarding La2Ce2O7 has so far been performed by researchers from Uni Oslo. With 0.24 mS×cm-1 at 550 °C, it shows a slightly lower proton conductivity than the best #perovskite, but higher chemical stability and a wide range of possible dopants.
Show threadKerstin NeuhausNov 24, 2023
This is, where our project begins: we would like to develop a doping strategy to reach a sufficiently high proton conductivity at T<250°C. The material can then be used for e.g. as electrolyte for small, sputterable on-chip batteries or fuel cells, or electro-chemo-mechanical actuators. 👩‍🔬🧪