Low thermal conductivity in a modular inorganic material with bonding anisotropy and mismatch

Blocking heat in two ways Low thermal conductivity is important for barrier coatings, thermoelectrics, and other applications. Gibson et al . combined two complementary methods that manipulate internal interface properties to dramatically decrease the thermal conductivity of the inorganic material BiO 2 Cl 2 Se (see the Perspective by Kim and Cahill). The authors took advantage of both in-plane structural distortions and weak bonding layers to push the conductivity down to 0.1 watts per kelvin per meter: only four times that of air. The principles should be applicable to other systems and provide a method for developing crystals with extremely low thermal conductivity. —BG