Electrical properties of Ba3C60 collapsed under high-pressure and high-temperature conditions

The barium doped fulleride Ba3C60 was treated under high-pressure and high-temperature conditions of 5–15 GPa and temperatures up to 1150 °C. Amorphous solids stable in air were obtained. The high micro Vickers hardness and the Raman spectra of the solids suggest that the C60 molecules are collapsed to form amorphous three-dimensional (3D) polymer encapsulating Ba atoms. The solids show a semi-metallic conductivity with a positive Hall coefficient. It is likely that barium atoms are trapped in the carbon network, replacing carbon atoms as clusters, and act as dopants for holes. The low electrical mobility of the solid is attributable to the lack of 3D periodicity of the polymer.