Electroceramics for fuel cells and batteries

Fast-ion conductors general comments The essential element of ceramics-based fuel cells and batteries is the electrolyte, a solid, fast-ion conductor. 

The precise structural conditions for fast-ion conduction have yet to be established (especially when the effects of microstructure are involved), but there 

The fast-ion ceramic conductors of interest here are cubic stabilized zirconia (CSZ), an oxygen ion conductor, and a sodium aluminate (/f -alumina), a sodium ion conductor. Both are discussed in detail below. The overview by T.A. Ramanarayanan et al. [8] covering CSZ and its applications is recommended. 

Cubic stabilized zirconia (CSZ) Pure zirconia (Zr02) is either chemically extracted and purified from the mineral zircon (ZrSi04) or purified from baddeleyite. It occurs as three crystalline polymorphs with monoclinic, tetragonal and cubic structures. The monoclinic form is stable up to 1170°C 

Cubic Zr02 has the fluorite structure with the O2- ions arranged in simple cubic packing and half the interstices in this lattice occupied by Zr4+ ions (Fig. 4.29) the substitution of lower-valence cations leads to O2- ion vacancies as indicated. The vacancies which stabilize the structure also lead to high mobility in the oxygen sub-lattice and to behaviour as a fast-ion conductor. 

---