Structural, Transport and Magnetic Properties of KxCoO2 (x = 0.36)

Layered potassium cobaltate K_xCoO₂ with x = 0.36 has been successfully synthesized in KOH fluxes at 480 degrees C, and its hydrated form K_0.36CoO₂.yH₂O (y<=0.8) has been obtained by intercalation with water. The diffraction peaks of K_0.36CoO₂ can be indexed by an orthorhombic cell similar to Na_0.5CoO₂, and K_0.36CoO₂.0.8H₂O is isostructural with its sodium analog, monolayer hydrate Na_xCoO₂.yH₂O. While the samples K_xCoO₂ and K_0.36CoO₂yH₂O (y<0.8) show semiconductor behaviour, a metal-insulator transition around 30 K was observed in the sample K_xCoO₂.0.8H₂O. Both the samples show complicated magnetic behaviour, and they are primarily paramagnetic in the range from 5 K to 300 K with a spin-glass-like transition around 56 K.