X-ray and neutron powder diffraction study of the monoclinic perovskites Sr2MSbO6 (M=In, Y)

The structures of the perovskites Sr2InSbO6 and Sr2YSbO6 have been investigated by X-ray and neutron powder diffraction. Both compounds are of monoclinic distortion, space group P21/n, with the lattice parameters related to that of the ideal cubic-perovskite (ap) by a≈b≈2ap, c≈2ap and β≈90°. The distortions that occur in Sr2InSbO6 and Sr2YSbO6 can be viewed as due to the octahedral tilts around both the two-fold [110]p- and the four-fold [001]p-axis of the cubic aristotype with the oxygen's shifted away from the In/Y(III) ions towards the Sb(V) ions, creating an ordered arrangement of the alternating InO6/YO6 and SbO6 octahedra.