EXTENDED X-RAY-ABSORPTION FINE-STRUCTURE STUDY OF THE POSITION OF ZR WITHIN THE UNIT-CELL OF SM2CO17

Extended x-ray-absorption fine-structure spectroscopy (EXAFS) has been used to determine the position of Zr within the unit cell of Sm2Co17. Induction-melted Sm2Co17:Zr ternary alloys, aged at 1180-degrees-C, then quenched, consisted of intimately mixed H2:17 and R2:17 having Zr in solid solution as well some regions of R2:17 that were poor in Zr. EXAFS spectroscopy of these specimens indicates that the most probable position for Zr is a site having 2 Sm near-neighbor atoms and 11 Co atoms distributed over three different interatomic distances. This is consistent with a direct substitution of Zr for Co in the Co site in the mixed planes (12j in P6(3)/mmc or 18f in R3m).