Study of flux growth of Cr-containing borates and oxyborates under the conditions of low Cr2O3 solubility

Abstract

With the type, size and quality of experimental samples playing a special role in searching for new materials, single crystal samples are of high value and methods of their fabrication have to be developed and constantly improved, to be adjusted to the peculiarities of an expected compound. The flux technique for producing chromium-containing materials is characterized by the low solubility of Cr₂O₃ used. The study deals with crystallization of Cr-containing borates HoCr₃(BO₃)₄ with a huntite structure and oxyborates Cu₂CrBO₅ with a ludwigite structure in flux systems based on Li₂WO₄. Consideration is given not only to the possibility of growing sizable single crystals of these compounds, but also to a mixed huntite–ludwigite flux system intended to unify the growth technology and to identify the phase boundary of these compounds. The investigation of the phase diagram allowed the secondary phases to be found and analyzed. Powder and single crystal X-ray diffraction and element-sensitive EDX techniques were used to control the composition and structure of the obtained compounds. Orientational thermal and field dependences of magnetization of the obtained crystals HoCr₃(BO₃)₄ and Cu₂CrBO₅ were measured.