High-contrast, reversible change of thermal conductivity in hexagonal nickel-iron sulfides

Abstract Materials showing abrupt change of thermal conductivity are strongly desired for rapidly developing thermal regulation applications. Here, we report a sharp change of thermal conductivity (Δκ/κ0) up to 200% within a temperature interval of ~ 40 K in hexagonal sulfides Ni1-xFexS bonded with silver. Such Δκ/κ0 values exceed those reported in other thermal regulation materials, e.g., VO2 series (Δκ/κ0