Low thermal conductivity of CsBiNb2O7 epitaxial layers

The thermal conductivity of an epitaxial layer of CsBiNb2O7 grown by pulsed-laser deposition is measured by time-domain thermoreflectance in the temperature range 100<T<600 K. Characterization by x-ray diffraction and cross-sectional transmission electron microscopy show that the sample has the n=2 structure of the Dion–Jacobson series of phases. The conductivity of this layered oxide is ≈60% of the predicted minimum thermal conductivity in this temperature range; the thermal conductivity at room temperature, 0.4 W m−1 K−1, is comparable to the lowest conductivity ever observed in an oxide crystal.