EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE AND PERTURBED-ANGULAR-CORRELATION STUDY OF IMPURITY CLUSTERING IN DILUTE NICKEL-ALLOYS

We report on an experimental study of indium and niobium impurity dist ributions in NiNbIn dilute alloys by combining the perturbed-angular-c orrelation (PAC) technique with extended x-ray-absorption fine-structu re (EXAFS) measurements on both the indium and niobium K edges at room temperature. Our EXAFS results show that around the indium or niobium central atom, the first-shell coordination number is strongly reduced with respect to a pure nickel environment. Whereas niobium is found i n the first shell around niobium in small cluster configurations, indi um is found at larger distances from indium indicating a repulsive In- In interaction. No close mixing between these two impurities was detec ted, confirming the strong In-Nb repulsion. These findings are fully c onsistent with the conclusions drawn from the data obtained in an earl ier as well as the present PAC study.