Order and Disorder in Transition Metal Carbides and Nitrides: Experimental and Theoretical Aspects

摘要

Many carbides and nitrides of transition metals can be described as a close-packed metal lattice (f.c.c. or h.c.) with the carbon or nitrogen atom in the center of the octahedral interstices. If these octahedal sites are not all occupied, the unoccupied sites may be considered as ''vacancies'' in the metalloid sublattice. Depending on the composition and the thermal treatment, these ''vacancies'' may be found ordered (forming a sublattice) or disordered. ''Vacancies'' and metalloid atoms form a pseudo ''solid-solution'', with order-disorder phenomena analogous to those encountered in metallic solid solutions Asub(1-x)Bsub(x). Recent results are reviewed: order-disorder transitions are studied by neutron diffraction at high temperature and short-range order by diffuse neutron scattering. A theoretical interpretation of results is briefly presented. (ERA citation 10:044661)