Original disorder–order transition related to electronic and magnetic properties in the thermoelectric misfit phase [Ca2CoO3][CoO2]1.62

A structural phase transition is shown around 400 K for the thermoelectric lamellar misfit cobalt oxide [Ca2CoO3][CoO2]1.62. This transition is related to a rearrangement of the central [CoO] layer of the [Ca2CoO3] slab of this structure, characterized by a commensurate intrinsic modulation q 2 = 2\over 3a * − 1\over 3c *. The partial residual disorder related to split Co and O atomic sites along the misfit b direction disappears and one can describe this layer with its triple chains as a modulated configuration with a regular and not distorted periodicity along b. This phase transition is associated with small changes observed in the transport and magnetic properties as a function of temperature.