Ordered rock-salt related nanoclusters in CaMnO2.
Oxygen engineering techniques performed under adequate controlled atmosphere show that the CaMnO(3)-CaMnO(2) topotactic reduction-oxidation process proceeds via oxygen diffusion while the cationic sublattice remains almost unaltered. Extra superlattice reflections in selected area electron diffraction patterns indicate doubling of the CaMnO(2) rock-salt cell along the cubic directions of a distorted rhombohedral cell originated by ordering of Ca(2+) and Mn(2+) ions distributed in nanoclusters into a NaCl-type matrix, as evidenced by dark field electron microscope images. The local nature of the information provided by the transmission electron microscopy techniques used to characterize the rock-salt type Ca(1-x)Mn(x)O(2) solid solution clearly hints at the existence of subtle extra ordering in other upper oxides of the Ca-Mn-O system. The combination of local characterization techniques like electron microscopy with more average ones like powder X-ray and neutron diffraction allows a very complete characterization of the system.
Varela
Aurea
A
Departamento de Química Inorgánica, Facultad de Químicas, Universidad Complutense de Madrid, E-28040-Madrid, Spain.
de Dios
Susana
S
Parras
Marina
M
Hernando
María
M
Fernández-Díaz
M Teresa
MT
Landa-Cánovas
Angel R
AR
González-Calbet
José M
JM