Crystallization of La2Cu2O5 has been investigated in the La2O3-CUO system for various starting compositions both in air and oxygen atmospheres. In air, we find that there exists a new region of crystallization of La8Cu7O19 phase, just above that of La2Cu2O5. However, this region vanishes completely in flowing-oxygen atmosphere. By utilizing this, large single crystals of the 4-leg spin-ladder compound La2Cu2O5 have been successfully grown from CuO flux by the slow cooling method. Room-temperature resistivity parallel to the ladder direction (∥b) of the as-grown crystals is estimated to be 1.7×103 Ω cm. A significant decrease in the resistivity (798 mΩ cm at 300 K) is observed upon hole doping by means of high oxygen pressure annealing (approximately 400 atm) using a hot isostatic pressing furnace. However, no transition was observed from the semiconducting behavior.
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