Structural and physical properties of CaFe2As2

Polycrystalline and single crystalline samples of CaFe2As2 were prepared by using different fabrication routes. These samples show evident differences in both phase transition temperatures and transport properties depending on fabrication conditions. TEM observations reveal a rich variety of structural phenomena in these materials, such as a tweed-like pattern in self-flux samples, a structural modulation along the < 1 1 0 >(tetra) direction in the polycrystalline sample, and complex dislocation networks in the Sn-flux samples. Careful analysis shows that the twinning domains arising from the tetragonal-to-orthorhombic phase transition belong to the delta-type. (C) 2010 Elsevier Ltd. All rights reserved.