Electroceramics PDF

ABSTRACT

A strategy is defined for investigating and establishing structure-property relationships in electroceramics, with particular attention to the influence of crystal structure on the ferroelectric properties of perovskites. The geometrical constraints of the perovskite structure, of composition AB03, dictate that there are only three structural degrees of freedom: ionic displacement, anionic polyhedral distortion and octahedral tilting. The relative importance of each of these for the occurrence of ferrolectric properties is brought out, with the polyhedral volume ratio, VA: VB introduced as a unifying structural determinant. The quantitative relationships between VA: VB and tilting in rhombohedral and orthorhombic perovskites are described, and a method defined for the prediction of new ferroelectric-piezoelectric ceramic compositions. A novel interpretation of the PZT phase diagram is given, with an extension of the methodology to related structural systems, Aurivillius phases and layered (slab-like) perovskites outlined. Both systems are potential piezoelectric materials for use at elevated temperatures. The effect of doping on the stability of alternative perovskite phases is also relevant to the cathodes and interconnects currently employed in solid oxide fuel cells.

Edited by: W. E. Lee, A. Bell