Research paperLow temperature transport properties of pyrolytic graphite sheet

- We characterized transport properties of Pyrolytic Graphite Sheet (PGS).
- Thinner PGS has higher crystallinity and higher electrical/thermal conductivities.
- Electrical and thermal conductivities of graphite-family have some relationship.
- PGS is advantageous for applications as a thermal link at 60-300 K.

We have made thermal and electrical transport measurements of uncompressed pyrolytic graphite sheet (uPGS), a mass-produced thin graphite sheet with various thicknesses between 10 and 100 μm, at temperatures between 2 and 300 K. Compared to exfoliated graphite sheets like Grafoil, uPGS has much higher conductivities by an order of magnitude because of its high crystallinity confirmed by X-ray diffraction and Raman spectroscopy. This material is advantageous as a thermal link of light weight in a wide temperature range particularly above 60 K where the thermal conductivity is much higher than common thermal conductors such as copper and aluminum alloys. We also found a general relationship between thermal and electrical conductivities in graphite-based materials which have highly anisotropic conductivities. This would be useful to estimate thermal conductance of a cryogenic part made of these materials from its electrical conductance more easily measurable at low temperature.