Principal Investigator Harry Tuller
Most structural ceramics are known for their high resistance to charge transfer, and are therefore useful as electric insulators. Some electroceramics, however, are very useful for the exact oposite reason - they can accomodate charge transfer. Semiconducting ceramics, just like silicon and III-V materials, can be either p-type or n-type. Their electrical conductivity often depends on oxidation-reduction reactions with the surrounding enviroment; these materials are highly useful as chemoresitive gas sensors.
Ionic conduction is achieved by the movement of ions (atoms of positive or negative charge) through the solid. This transfer is usually done via point defects called vacancies in the crystal lattice. Such movement can require high energy, making ionic conduction very strongly dependent on temperature. Ionic conductors are useful in gas sensors, fuel cells, and batteries.
Materials that can accomodate electron conductivity as well as ionic conductivity are known as mixed conductors, and are particularly useful as solid oxide fuel cell (SOFC) electrodes.