The Hall Effect of the Polyvinyl Chloride Char

The thin plates of polyvinyl chloride char in which the nongraphitic pitch binder of usual carbon prodact was absent were prepared by the carbonization in the narrow spacing between two quartz plates. They were heat-treated at various temperatures. The Hall coefficient and the lattice constant of them were measured at the room temperature. The heat-treatment temperature dependence of the Hall coefficient was the same as those of typical soft carbons.In order to explain the variation of the Hall coefficient, it is assumed that the two dimensional Brillouin zone and the two dimensional Fermi surface (Fermi curve) exist in the substances which were heat-treated in the temperature range from 900°C to 1900°C. The existence of electron-like carriers and hole-like carriers was assumed. The sign of the Hall coefficient was interpreted in terms of the length of the Fermi curve. The three dimensional Brillouin zone and the three dimensional Fermi surface were assumed for the specimens which were heat-treated above 2000°C. The rapid decrease and the change of sign of the Hall coefficient at the heat-treatment temperature of nearly 2100°C were associated with the overlapping of electrons across the zone boundaries.