Phase transition, thermal expansion and electrical properties of BiCu2VO6

Phase transition in BiCu2VO6 has been studied by variable temperature powder and single crystal X-ray diffraction. A reversible single-crystal-to-single-crystal phase transition has been identified and the high-temperature β-BiCu2VO6 polymorph structurally characterized. β-BiCu2VO6 is monoclinic I-centered and related to the α-form by a subgroup–supergroup relationship. Bi atoms are coordinated to oxygen so as to give rise to (BiO2)− chains parallel to the c-axis. The magnetic Cu–O sublattice forms a complex system of quasi one-dimensional ladders, built up by five- and six-coordinate Cu atoms. Dynamic disorder in the high temperature structure can be described in terms of librational motion of VO4 tetrahedral group. AC impedance measurements suggest predominantly electronic conduction in this material.