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Raman spectroscopy of M3B7O13X boracites (M = Cr,Co,Ni,Cu,Zn,Cd; X = Cl,Br,I)


  • Milko N. Iliev,

    Corresponding author
    1. Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, TX, USA
    • Correspondence to: Milko Iliev, Texas Center for Superconductivity, University of Houston, Houston, TX 77204-5002, USA.


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  • Hans Schmid

    1. Department of Inorganic, Analytical and Applied Chemistry, University of Geneva, Geneva 4, Switzerland
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We report results of a Raman study on single crystals of 16 boracites M3B7O13X (M = Cr,Co,Ni,Cu,Zn,Cd; X = Cl,Br,I) over a broad temperature range. The Raman modes for all boracites in their high-temperature prototype cubic (Fmath formula3c) phase are compared. With decreasing temperature, most (but not all) compounds present a transition to the low-temperature orthorhombic phase (Pca21) or to a sequence of orthorhombic, monoclinic (Pa), and trigonal (R3c) phases. The variations of the Raman spectra through different phases are studied in detail. Special attention is paid to the temperature hysteresis near the transitions and the dependence of transition temperature on the direction of crystal growth for the same material. Copyright © 2014 John Wiley & Sons, Ltd.