Dependence of superconducting properties of undoped Bi2201 single crystals on conditions of their free growth in gas-filled cavities of a molten salt

High-quality undoped Bi2201 single crystals were obtained by free growth in gas-filled cavities formed in the volume of a KCl melt. The superconducting transition temperature Tc was found to be affected by the crystallization temperature Tcryst and varied from 10 to 2 K as Tcryst increased from 840 to 860 °C. The crystals with the highest Tc both in the underdoped and overdoped states were near the maximum of doping curve.