X-ray diffuse scattering from β'-AgZn alloy

Measurements were made of X-ray diffuse scattering from quenched AgZn single crystals which are in a metastable beta '-phase state having the B2-type structure. Two notable features were found in the distributions of diffuse scattering intensity: one is intensity streaks running through the fundamental reflection points in the (110) and its equivalent directions and the other is intensity sheets extending uniformly parallel to the (111) and its equivalent reciprocal lattice (REL) planes. The former is the diffuse scattering often observed in the B2 alloys and is associated with the (110) (110) transverse acoustic phonons. The latter shows the presence of random displacements of the (111) atom rows in the (111) direction. The structural relationship between the beta ' and the stable zeta phase suggests that the displacements are a precursive fluctuation of the beta ' to zeta transition, but the temperature dependence of the intensity of the (111) sheets show that they are purely thermal in their origin.