Single crystal growth and physical properties of carbon-substituted YBa₂Cu₃O_7-δ

Single crystals of C-substituted YBa₂Cu₃O _7-δ (C-YBCO) were prepared by changing atmosphere in a growing process. With increasing the CO₂ concentration in the atmosphere, the carbon content in a crystal increases, and the c-axis length decreases. From the T_c change under various annealing conditions and the magnetic susceptibility results, it was found that C-YBCO does not enter the carrier-overdoped region, while the non-substituted samples can. It suggests that the carbon substitution disturbs the oxygen diffusion, resulting in a suppression of carrier doping.