STRUCTURAL CHARACTERIZATION AND PROPERTIES OF THE PEROVSKITE (NALA)(MW)O-6 (M=CO, NI) - 2 NEW MEMBERS IN THE GROUP-SUBGROUP RELATIONS FOR THE PEROVSKITE-TYPE STRUCTURES

The crystal structures of (NaLa)(MW)O-6 (M = Co, Ni) suggest that both adopt a monoclinic perovskite-type structure [M = Co: a = 5.546(3), b = 5.545(4), c = 7.903(6) Angstrom, beta = 89.99(3)degrees; M = Ni: a = 5.517(5), b = 5.518(7), c = 7.862(2) Angstrom, beta = 90.02(4)degree s; space group P2(1)/m]. The structure consists of an ordered arrangem ent of MO6 and WO6 octahedra (in B sites) which share corners and alte rnate planes of La and Na cations along the c-axis (in A sites). This structure is analysed on the basis of a general group subgroup symmetr y relationship for some perovskites that were previously described, an d the electronic and magnetic properties of both compounds are discuss ed.