Chemistry of polar intermetallic compounds. Study of two zirconium-antimony (Zr5Sb3) phases, hosts for a diverse interstitial chemistry

Abstract

A variety of synthesis routes, some phase properties, and two single-crystal x-ray studies have established something of the nature of the Zr-Sb system in the neighborhood of 65 atom % zirconium. Samples prepared by vapor-phase transport or by annealing either elemental powders or arc-melted products at 1000-1100/degree/C yield the Mn/sub 5/Si/sub 3/ form of Zr/sub 5/Sb/sub 3+x/. This is true binary phase that is nonstoichiometric over the range of 0.0/sub 0/ /le/ x /le/ 0.4/sub 2/. Study of a single crystal with x = 0.16 (1) from an arc-melted sample has established that the extra antimony in this structure is bonded in an interstitial site in the center of a chain of confacial zirconium octahedra (space group P6/sub 3//mcm, Z = 2, a = 8.4267 (5) /angstrom/, c = 5.7856 (6) /angstrom/, R = 2.7%, R/sub w/ = 3.4%). Many other atoms may also be bound at this site. Binary Zr-Sb samples in the range 0 /le/ x /le/ /approx/ 0.2 melt incongruently to form the foregoing phase plus a second, new, high-temperature, stoichiometric form of Zr/sub 5/Sb/sub 3/ in the Y/sub 5/Bi/sub 3/ structure (space group Pnma, Z = 4, a = 7.465 (1) /angstrom/, b = 8.801 (1)more » /angstrom/, c = 10.865 (2) /angstrom/, R = 2.8%, R/sub w/ = 2.9%). The two structure types are further described and compared. 22 references, 6 figures, 5 tables.« less