TY - JOUR
T1 - Crystal structures of disordered A2Mn3+M5+O6 (A=Sr, Ca; M=Sb, Nb, Ru) perovskites
AU - Lufaso, Michael W
AU - Woodward, Patrick M
AU - Goldberger, Joshua
N1 - Polycrystalline samples of A 2Mn MO 6 ( A=Sr, Ca; M=Nb, Sb, Ru) were prepared by conventional solid state synthesis and their crystal structures were determined using neutron powder diffraction data. All six compounds can be classified as distorted, disordered perovskites. The Mn 3+/ M 5+ distribution is disordered in all six compounds.
PY - 2004/4/1
Y1 - 2004/4/1
N2 - Polycrystalline samples of A2MnMO6 (A=Sr, Ca; M=Nb, Sb, Ru) were prepared by conventional solid state synthesis and their crystal structures were determined using neutron powder diffraction data. All six compounds can be classified as distorted, disordered perovskites. The Mn3+/M5+ distribution is disordered in all six compounds. The strontium containing compounds, Sr2MnMO6 (M=Nb, Sb, Ru), undergo out of phase rotations of the octahedra about the c-axis (tilt system a0a0c−) leading to tetragonal I4/mcm space group symmetry. The calcium containing compounds, Ca2MnMO6 (M=Nb, Ru, Sb), have orthorhombic Pnma space group symmetry, as a result of a GdFeO3-type octahedral tilting distortion (tilt system a−b+a−). A cooperative Jahn–Teller distortion is observed in Sr2MnSbO6 and Sr2MnRuO6, but it is much smaller than the distortion observed in LnMnO3 (Ln=lanthanide ion) perovskites. It is possible that Jahn–Teller distortions of the MnO6 octahedra take place on a short-range length scale in the other four compounds, but there is little or no evidence for cooperative ordering of the local distortions. These findings demonstrate a link between orbital ordering, cation ordering and octahedral tilting.
AB - Polycrystalline samples of A2MnMO6 (A=Sr, Ca; M=Nb, Sb, Ru) were prepared by conventional solid state synthesis and their crystal structures were determined using neutron powder diffraction data. All six compounds can be classified as distorted, disordered perovskites. The Mn3+/M5+ distribution is disordered in all six compounds. The strontium containing compounds, Sr2MnMO6 (M=Nb, Sb, Ru), undergo out of phase rotations of the octahedra about the c-axis (tilt system a0a0c−) leading to tetragonal I4/mcm space group symmetry. The calcium containing compounds, Ca2MnMO6 (M=Nb, Ru, Sb), have orthorhombic Pnma space group symmetry, as a result of a GdFeO3-type octahedral tilting distortion (tilt system a−b+a−). A cooperative Jahn–Teller distortion is observed in Sr2MnSbO6 and Sr2MnRuO6, but it is much smaller than the distortion observed in LnMnO3 (Ln=lanthanide ion) perovskites. It is possible that Jahn–Teller distortions of the MnO6 octahedra take place on a short-range length scale in the other four compounds, but there is little or no evidence for cooperative ordering of the local distortions. These findings demonstrate a link between orbital ordering, cation ordering and octahedral tilting.
KW - Cooperative Jahn–Teller distortions
KW - Cation ordering
KW - Orbital ordering
KW - Neutron powder diffraction
KW - Perovskites
KW - Octahedral tilting
UR - http://www.sciencedirect.com/science/article/pii/S0022459604000027
U2 - 10.1016/j.jssc.2003.12.020
DO - 10.1016/j.jssc.2003.12.020
M3 - Article
SN - 0022-4596
VL - 177
JO - Journal of Solid State Chemistry
JF - Journal of Solid State Chemistry
ER -