Ordered Alloys of the Gold-Palladium System. II. Electron Diffraction Study on Evaporated AuPd3 Films

Gold-palladium alloys, ranging around AuPd 3 in composition, were studied by electron diffraction using evaporated single crystal films, and a superlattice AuPd 3 was found. The temperature of order-disorder transformation was estimated at about 780°C for the alloy with a composition of about 80 at. % palladium. The electron diffraction pattern of the ordered alloy AuPd 3 showed that the intensities of the superlattice reflections were extremely weak, though they were sharp. The results mean that the degree of order is of a very reduced value. This special nature of the ordered alloy AuPd 3 is discussed by comparing to other ordered alloys of the noble metal-palladium systems.