A NEW 123 FAMILY - LNBA2FE3OZ .3. LN=GD

An electron diffraction and microscopy study performed on the system L nBa2Fe3Oz has shown the presence of new perovskite-related superstruct ures as a function of both Ln and oxygen stoichiometry. These material s constitute the members n = 1 (Ln = Dy, Ho), n = 3/2 (Ln = Gd), n = 4 /3 (Ln = Gd, when overheated at 1300-degrees-C for 15 days), and n = 2 (Ln = Nd) of a homologous series with the general formula Ln1/3Ba2/3F eO3-(1/2n+1). A modulated structural approach to LnBa2Fe3Oz over the d escription of these phases is discussed. (C) 1994 Academic Press, Inc.