Vanishing Superstructure: Crystal and Local Structures of Ni3 – xMTe2 (M = Sb, Sn)

Abstract

Series of compounds Ni3 – xMTe2 (M = Sb, Sn; x = 0–1) were obtained by high-temperature sealed-tube synthesis and characterized by X-ray powder diffraction and 121Sb and 119Sn Mössbauer spectroscopy. For Ni3–xSnTe2, it was shown that, as х varies from 1 to 0, nickel is distributed over three possible sites, two of which give a total occupancy of 1 and have ordered vacancies. Meanwhile, for Ni3–xSbTe2 and х other than ~0.9–1.0, the vacancy ordering disappears. The temperature dependence of the presence or absence of vacancy ordering was established for Ni2SbTe2; the ordering disappears on heating above 600°C and appears again on cooling.