Layered perovskite oxides: Synthesis, structural characteristics and electrical properties

The Aurivillius type oxides show a layered perovskite structure, built up by the interleaved of perovskite [A(0-1)B(n)O(3n-1)] and [Bi2O2] sheets. The structural stability of these oxides is presented as a function of the ionic radii and lone pair of electrons (ns(2)) of cations. New mechanochemical activation synthesis methods have been used in order to facilitate the preparation of Aurivillius phases and to cheapen their production systems. Some Aurivillius ferro-piezoelectric and ionic conductors examples are shown. The mesostructure and ferro-piezoelectric properties are improved by processing materials from mechanochemically activated amorphous powdered precursors. Change in unit-cell volume of these materials, by means of cationic substitutions, are responsible for the changes of their T-c. Ionic conductivity in Aurivillius oxides occurs by hopping between neighboring oxygen positions within perovskite layer while ion migration within bismuth layer would have a negligible contribution. Mechanical processes can recycle some of these materials, damaged by consecutive thermal treatments.