Growth and Electric Transport of Ca-doped PrBa2Cu3O7-δSingle Crystals

Abstract

Crystal growth of Ca-doped PrBa2Cu3O (Pr-123) single crystals by slow cooling of Pr3O11-CaCO3-BaCO3-CuO melts (self-flux technique) in ambient air atmosphere was studied. As the first approach the growth of Ca-free crystals in Al2O3 and ZrO2 crucibles was investigated. The best quality crystals with the average size of 5 x 5 x 0.2mm3 were obtained from Al2O3 crucibles for Ba/Cu = 0.41 and 15 wt.% (2.41 mol.%) of stoichiometric Pr-123 solute in the melt. Next, using CaCO3 as calcium source (0.09 -12.68 wt.%), the good quality Pr1-x CaxBa2Cu3O crystals with 0 ≤ x ≤ 0.26 were grown in the Al2O3 crucibles from the solution with fixed value of Ba/Cu = 0.41. The oxygenated single crystals with size up to 5 x 8 x 0.2 mm3 were used for electric transport investigations from four-probe resistivity measurements. The temperature dependence of resistivity of Ca-doped Pr-123 crystals is typical for systems with locallized states and, in principle, follows the Mott law for variable-range hopping (VRH).