Thermal conductivity measurements of PTFE and Al$_2$O$_3$ ceramic at sub-Kelvin temperatures

Understand

The design of low temperature bolometric detectors for rare event searches necessitates careful selection and characterization of structural materials based on their thermal properties.

• We measure the thermal conductivities of polytetrafluoroethylene (PTFE) and Al$_2$O$_3$ ceramic (alumina) in the temperature ranges of 0.17-0.43 K and 0.1-1.3 K, respectively.
• For the former, we observe a quadratic temperature dependence across the entire measured range.
• For the latter, we see a cubic dependence on temperature above ~0.3 K, with a linear contribution below that temperature.