New misfit-layered cobalt oxide (CaOH)1.14CoO2

We synthesized a new cobalt oxide (CaOH)1.14CoO2 by utilizing a high-pressure technique. X-ray and electron diffraction studies revealed that the compound has a layered structure that consists of CdI2-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.

Graphical abstractCrystal-structure model of the misfit-layered cobalt oxide (CaOH)1.14CoO2. The rectangles indicate unit cells of the two subsystems. The open circles and squares represent the cobalt atoms situated at different positions along the projected coordinate.Figure optionsDownload full-size imageDownload as PowerPoint slide