ORDERING AND DISORDERING IN (A'A'') (B'B'') O-3-TYPE PEROVSKITE COMPOUNDS

An empirical method is proposed to judge ordering or disordering in th e crystal structure of the (A'A '') (B'B '') O-3-type perovskite compo und through a simple calculation only using the atomic parameters of t he A' and A '' atom and the ionic parameters of the B' and B '' cation . The method has been used to judge ordering or disordering in the cry stal structure of 56 (A'A '') (B'B '') O-3-type perovskite compounds. Most judgements for the ordered or disordered structures of these comp lex perovskite compounds are in agreement with the experimental result s and there are only five exceptional compounds (about 9% of the 56 co mpounds) to this judgement method. This empirical method will be valid for the various complex perovskite compounds with an ordering or diso rdering structure. (C) 1998 Elsevier Science S.A. All rights reserved.