Electronic and physico-chemical behaviour of some lamellar compounds of graphite

Abstract

Some comparisons were made between the lamellar crystalline compounds of graphite and intercalary compounds formed of a certain number of other crysthls with shell structure. Although there is a certain number of resemblances, the graphite is almost unique with respect to the amphoteric character of its hexagonal lattices. They can be considered as aromatic macromolecules. In graphite, the interaction between these macromolecules is only weak. They preserve the essence of their aromatic structure in numerous crystalline compounds. Because of the aromatic character there is produced, in a distinct fashion, in the crystulline compounds a charge transfer between these macromolecules and various intercalary groups. This causes profound modifications in the electronic properties of solids. By interposing electron donor groups such as the atoms of an alkali metal or electron acceptor groups such as the halogens or acid radicals, a new class of very conductive solids is obtained. Anisotropic studies of the electrical properties of these solids parallel and perpendicular to the hexagonal layers of the carbon are analyzed. They give important information on the charge transfer to or from aromatic macromolecules. Impurities or crystalline faults of the original graphite modify the formation and the behavior of its crystalline compounds. Some impuritymore » atoms at the edges can facilitate the intercalation of groups in the crystalline compounds and can also affect the electron levels in the macromolecules of carbon, modifying as a result the free bonding energy. Lattice faults can seriously perturb the planeity of aromatic lattices because of the impurity atoms bound to a hold or a prominence of the lattice. Spiral dislocations of the lattice were detected in some graphites. It is unknown to what extent these faults or other faults can affect the conclusions, based on crystalline compounds. (tr-auth)« less