ELECTRONIC-STRUCTURE AND PROPERTIES OF AURIVILLIUS PHASES

The electronic structure of compounds from the family of Aurivillius p hases of the general formula Bi2O2[A(n-1)B(n)O(3n+1)], where n is the number of perovskite layers, was calculated by the ab initio LMTO-ASA method. For compounds with B = Nb, Ti; A = Ca,Sr, Ba, Bi, and n = 1,2, variations of the electronic structure and properties depending on th e number ofperovskite units and on the varieties of A and B cations we re studied. Effects of vacancy formation in the Bi2O2 layers and metal -oxygen planes are considered. The instability of Bi2NbO6 is explained , and favorable positions for oxygen replacement by fluorine are found . The possibility of superconductivity in these compounds is considere d.