Structure of perovskite type compounds, ALaMnTaO6 (A = Sr, Ba)

The crystal structure of ALaMnTaO(6) (A=Sr, Ba) have been determined from the powder X-ray diffraction data. The Rietveld refinement confirms that SrLaMnTaO6 is a monoclinic with the space group P2(1)/n, a =0.56939(1), b=0.57561(2), c=0.80750(2) nm and beta=89.99(1) deg. The deformation of oxygen octahedron was derived and the oxygen octahedron tilts against c-axis. The profile refinement of BaLaMnTaO6 shows that it has a structure of the (NH4)(3)FeF6-type, with the space group Fm (3) over bar m and the lattice parameter a=0.81752(2) nm. The ordered distribution of Mn and Ta ions over the B sites was derived in both compounds. (C) 1998 Elsevier Science S.A.