93 at.% of Na extraction from a Na24Si136 single crystal via anisotropic ion diffusion control method

An allotrope of Si, Si136, is a promising semiconductor for photovoltaics due to its direct bandgap. Si136 is synthesized via Na extraction from Na24Si136. In this study, 93 at.% of Na extraction from a single crystal of Na24Si136 was achieved using high-pressure-annealed zeolite as an ion absorber. The residual amount of Na is the least record among Na extraction from a single-crystalline Na24Si136. Na diffusion between the grains of amorphous phases of zeolite was suggested to be improved due to high-pressure annealing.