The crystallization region of La8Cu7O19 exists in a narrow temperature (1045 - 1050°C) and composition range (1:4.5-1:5.0; La2O3:CuO molar ratio) in the La2O3-CuO system in an air ambient. In this narrow range, we have succeeded in growing large La8Cu7O19 single crystals, for the first time, by a modified slow cooling method. Single-crystal X-ray diffraction analysis reveals that La8Cu7O19 crystallizes in a monoclinic structure with space group C2/c and has the lattice parameters a = 13.82(7) Å, b = 3.734(8) Å, c = 34.77(10) Å, and β = 99.3(4)°. The electrical transport behavior of the as-grown and hole-doped La8Cu7O19 single crystals are semiconducting. A lowest resistivity of 11.0 mΩ-cm is measured at 293 K along the ladder direction (∥ b-axis) for the hole-doped samples.
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