Superlattice presence in Cu₃Au and FeCo systems /

X-ray diffraction techniques have been widely used in establishing the presence of superlattice structures for alloy systems. In a superlattice structure the two atoms of a binary alloy occupy definite positions with respect to atoms of the companion species, in contrast to the usual random substitutional location of one atom in the structure of the other. For instance, in disordered Cu3Au, the gold atoms are arrayed randomly at sites normally occupied by copper atoms in the copper lattice, but in ordered Cu3Au all of the gold atoms are located at cube corners and copper atoms at face-centered positions of the unit-cell cube. Transformations from one state into the other can be invoked by suitable thermal treatment. The diffraction patterns for the two states will differ markedly depending upon the degree of ordering and the relative scattering power of the individual atomic species. Many systems such as CuZn, FeCo, etc., are difficult to study with x-rays since the scattering amplitudes for x-rays of the two atoms are so similar in value. It seemed of interest to study such systems by neutron diffraction where the scattering amplitudes might be more favorable.Work performed at the Oak Ridge National Laboratory."Date Declassified: June 17, 1948""AECD-2077"X-ray diffraction techniques have been widely used in establishing the presence of superlattice structures for alloy systems. In a superlattice structure the two atoms of a binary alloy occupy definite positions with respect to atoms of the companion species, in contrast to the usual random substitutional location of one atom in the structure of the other. For instance, in disordered Cu3Au, the gold atoms are arrayed randomly at sites normally occupied by copper atoms in the copper lattice, but in ordered Cu3Au all of the gold atoms are located at cube corners and copper atoms at face-centered positions of the unit-cell cube. Transformations from one state into the other can be invoked by suitable thermal treatment. The diffraction patterns for the two states will differ markedly depending upon the degree of ordering and the relative scattering power of the individual atomic species. Many systems such as CuZn, FeCo, etc., are difficult to study with x-rays since the scattering amplitudes for x-rays of the two atoms are so similar in value. It seemed of interest to study such systems by neutron diffraction where the scattering amplitudes might be more favorable.Mode of access: Internet