Thermopower of beech wood biocarbon

This paper reports on measurements of the thermopower S of high-porosity samples of beech wood biocarbon with micron-sized sap pores aligned with the tree growth direction. The measurements have been performed in the temperature range 5–300 K. The samples have been fabricated by pyrolysis of beech wood in an argon flow at different carbonization temperatures (Tcarb). The thermopower S has been measured both along and across the sap pores, thus offering a possibility of assessing its anisotropy. The curves S(Tcarb) have revealed a noticeable increase of S for Tcarb 1000°C) type. The existence of this transition is attested also by the character of the temperature dependences S(T) of beech wood biocarbon samples prepared at Tcarb above and below 1000°C.