Mixed conductors, also known as mixed ion-electron conductors (MIEC), are a single-phase material that has significant conduction ionically and electronically. Due to the mixed conduction, a formally neutral species can transport in a solid and therefore mass storage and redistribution are enabled. Mixed conductors are well known in conjugation with high-temperature superconductivity and are able to capacitate rapid solid-state reactions.
They are used as catalysts (for oxidation), permeation membranes, sensors, and electrodes in batteries and fuel cells, because they allow for rapidly transducing chemical signals and permeating chemical components.
Strontium titanate (), titanium dioxide (), , cerium(IV) oxide (), lithium iron phosphate (), and  are examples of mixed conductors.