New misfit-layered cobalt oxide (CaOH)1.14CoO2

We synthesized a new cobalt oxide (CaOH)(1.14)CoO2 by utilizing a high-pressure technique. X-ray and electron diffraction studies revealed that the compound has a layered structure that consists of Cdl(2)-type CoO2 layers and rock-salt-type double CaOH atomic layers. The two subcells have incommensurate periodicity along the a-axis, resulting in a misfit-layered structure. From resistivity and Seebeck coefficient measurements, we have shown that the two-dimensional (2-D) variable-range hopping (VRH) regime with hole conduction is dominant at low temperature for this compound. As temperature increases, the conduction mechanism undergoes crossover from the 2-D VRH regime to a thermal activation-energy-type regime. (c) 2006 Elsevier Inc. All rights reserved.