Synthesis and characterization of hexagonal Cd₅₁Yb₁₄ single crystals

Abstract

Synthesis of large, bulk single grains of the hexagonal crystalline phase Cd₅₁Yb₁₄ has been accomplished using the Bridgman method. Growth was carried out under controlled solidification conditions in sealed Ta crucibles, which maintain compositional integrity by eliminating evaporative losses of Cd and reaction with the containment material. Compositional analysis of the as-grown phase indicates no evidence of macrosegregation along the length of the crystal. High-resolution transmission electron microscopy (TEM) characterization of the hexagonal phase is hampered by the enhanced atmospheric reactivity of the higher Yb content of the hexagonal phase. Such a high sensitivity to ambient exposure was not observed during the recent synthesis and TEM studies of the quasicrystalline Cd_5.7Yb or cubic approximate phase Cd₆Yb. TEM and X-ray transmission diffraction results taken at the Advanced Photon Source at Argonne National Laboratory show the presence of a fine-structured second phase, which is randomly oriented throughout the matrix. The precipitates have been identified as pure Cd by d-spacing comparisons and likely form by selective atmospheric oxidation of Yb from the Cd₅₁Yb₁₄ phase.

Acknowledgement

This work was supported by the Office of Basic Energy Sciences, Materials Sciences Division of the US Department of Energy under contract no. W-7405-ENG-82.