Features of electrical properties of BE-C(Fe) biocarbons carbonized in the presence of an Fe-containing catalyst

The effect of partial graphitization on electrical and galvanomagnetic properties of BE-C(Fe) biomorphic carbons produced by beech wood carbonization at temperatures of 850–1600$^\circ$C in the presence of an iron-containing catalyst is studied. The use of an Fe catalyst at $T_{\operatorname{carb}}\ge$ 1000$^\circ$C leads to the formation of nanoscale graphite-phase inclusions; its total volume and nanocrystallite sizes increase with $T_{\operatorname{carb}}$. The data on the carrier concentration and mobility are obtained. It was shown that partially graphitized BE-C(Fe) carbons with $T_{\operatorname{carb}}\ge$ 1000$^\circ$C in the conductivity type and magnetoresistance features relate to highly disordered metal systems whose conductivity can be described taking into account the contribution of quantum corrections, mainly the correction caused by the electron–electron interaction. It is shown that nonmonotonic dependences of the Hall constant $R$ on the magnetic field are characteristic of BE-C(Fe) samples with 1000 $\le T_{\operatorname{carb}}<$ 1600$^\circ$C, which is most probably caused by the contribution of various carrier groups, i.e., electrons and holes. In BE-C(Fe) samples with $T_{\operatorname{carb}}$ = 1600$^\circ$C, the Hall coefficient corresponds to the metal state, which is associated with conducting medium homogenization resulting from the formation of a significant graphite phase volume.