A series of Nb3(Al Ge) alloys having the A15 crystal structure have been examined by X-ray-diffraction methods to determine the long-range order present in the alloys and the effects of heat-treatment upon it. Five different ordered structures may occur in the alloy Nb3(Al0.75 Ge0.25).The results show that two of these structures are the most likely to occur. Alloys of other compositions exhibit varying degrees of long-range order, influencing the superconducting transition temperature. Heat-treatment at 750° C for 20 h is sufficient to produce the most ordered structure.
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