Structural, Transport and Magnetic Properties of K_xCoO₂ (x=0.36)

Layered potassium cobaltate K_xCoO₂ with x=0.36 has been successfully synthesized in KOH fluxes at 480°C , and its hydrated form K_0.36CoO₂`yH<sub>2</sub>O (y≤0.8) has been obtained by intercalation with water. The diffraction peaks of K<sub>0.36</sub>CoO<sub>2</sub> can be indexed by an orthorhombic cell similar to Na<sub>0.5</sub>CoO<sub>2</sub>, and K<sub>0.36</sub>CoO<sub>2</sub>`0.8H₂O is isostructural with its sodium analog, monolayer hydrate Na_xCoO₂`yH<sub>2</sub>O. While the samples K<sub>x</sub>CoO<sub>2</sub> and K<sub>0.36</sub>CoO<sub>2</sub> yH<sub>2</sub>O (y <0.8) show semiconductor behaviour, a metal-insulator transition around 30K was observed in the sample K<sub>x</sub>CoO<sub>2</sub>`0.8H₂O. Both the samples show complicated magnetic behaviour, and they are primarily paramagnetic in the range from 5K to 300K with a spin-glass-like transition around 56K.