Structural and compositional investigations of Zr4Pt2O: A filled-cubic Ti2Ni-type phase

Syntheses, structural and compositional analyses of the filled cubic Ti2Ni-type phase in Zr-Pt-O system have been studied, largely for the platinum-richer compositions. Diffraction quality crystals were grown by annealing an arc-melted composition Zr4Pt2O0.66 at 1600 deg. C under Ar. The refined composition Zr4.0Pt1.95(1)O0.93(6) (a=12.5063(6) A, Fd3-barm, Z=16) is close to the idealized composition Zr4Pt2O known in several other Zr-T-O systems (T=late 4d or 5d transition element). (This composition has been erroneously reported by ICDD for years as Zr6Pt3O (No. 00-017-0557) and referred to as ε-Zr6Pt3O.) The product is only marginally poor in platinum and oxygen, in contrast to the 1960 reports of metallographic studies (∼Zr4Pt1.62O0.44). Under arc-melting conditions, high yields of the cubic phase are obtained from samples with lower platinum concentrations (Zr4Pt1.74O1.04), whereas samples near the refined cubic composition contain hexagonal Zr5Pt3Ox as well (Mn5Si3-type). The hexagonal structure of binary Zr5Pt3 was also refined (Mn5Si3 type, P63/mcm, a=8.210(1) A, c=5.385(2) A) and shown to be non-stoichiometric to at least Zr5Pt2.5. - Graphical abstract: The figure shows the environments of three atom types in the corrected structure, an oxygen-stuffed Ti2Ni type.