Grain boundary engineering for humidity sensing high entropy ceramics

High-entropy ceramics gain increasing attention over the last 20 years due to their ability to combine the favourable properties of their constituent elements. Entropy effects stabilize a simple crystal structure with near equal amounts of 5 or more component elements distributed homogeneously throughout the lattice. These materials have shown increased thermal and environmental stability, interesting electrical and dielectric and catalytic properties. In this study the microstructure of a barium titanate based ceramic with a simple cubic structure that shows unexpected electrical conductivity response in the presence of humidity will be characterized.

The observed fast, reversible change in the capacitance of over 2 orders of magnitude in 800 seconds when humidity was introduced to the atmosphere. It has been speculated an increase in the OH concentration in the crystal lattice or along the grain boundaries causes the increased conductivity. The fast reversibility is yet to be understood but has high potential for industrial humidity sensing applications.