Structure of the sigma-phase in the iron-chromium and cobalt-chromium systems

Abstract

THE application of X-ray single-crystal and powder methods has shown that the σ-phase structure is based on a tetragonal unit cell, containing 30 atoms, with space group P 4/mnm, P 4mn or P &4bar;n2. For the σ-phase of iron-chromium, a Combining double low line 8.790 A., c Combining double low line 4.559 A. This cell is not the same as found by Duwez and Baen1 using powder methods only. © 1951 Nature Publishing Group.