Electrical Transport Properties of Graphite Assuming Lattice Scattering

The theory for acoustical phonon scattering in graphite is combined with the appropriate electron band model and the transport theory based on the relaxation-time approximation to calculate electrical conductivity and thermoelectric power along the ab planes. Contributions from both majority and minority carriers are included. Basal-plane electrical conductivity and thermoelectric power data from 50 to 600 ^∘{}K for well-oriented graphite materials are analyzed. Assuming presently accepted values for electron band parameters, including a negative value for γ₂, data for the thermoelectric power cannot be explained as long as the material is considered to be an ideal graphite. Data above 300 ^∘{}K can be fit very well if an acceptor density of 2.2×{}10¹⁹ cm^-3 is assumed with an energy level of 0.01 eV below the majority bands at kz=±πc₀. Calculated results below room temperature with this acceptor density agree qualitatively with experiment. It is therefore concluded that either well-ordered graphite materials have {≈} 1 impurity (or defect) for every 10⁴ carbon atoms which acts as an acceptor, or refinement of the analytical approach is required, including the possibility of considering different values for band parameters.