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

Abstract

Crystal growth of Ca‐doped PrBa2Cu3O 7‐ δ (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 7‐ δ 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).

Surface morphology of PrBa2Cu3O7-δ single crystals after the long-lasting high-temperature reduction

“…The PrBa 2 Cu 3 O 7¡± crystals were obtained by the self-°ux method well described in [22,23]. The as-grown single crystals with the size up to 4 £ 6 £ 0:2 mm 3 were annealed in the argon and oxygen atmosphere in di®erent thermal conditions, that is, reduced for 1{2 hours at 900{1000 ± C in Ar, cooled to the room-temperature and oxygenated for 72 hours at 350 ± C.…”