Intragranular Critical Current Density in YBCO Substituted with Pr or/and Ca

The effect of magnetic (Pr) and non‐magnetic (Ca) chemical substitutions on the intragranular critical current, Jintra,c, in polycrystalline Y1−x−yPrxCayBa2Cu3O7−δ samples is studied. In principle two factors limit the Jintra,c: decoupling critical current density J0∼Hc/λ (Hc—thermodynamical critical field, λ‐London penetration depth) and pinning force. It is shown that at 4.2 K and low concentration (x = 0.05, y = 0 and x = 0, y = 0.025) both substitutions are almost equally effective and lead to Jintra,c higher than that for the non‐substituted sample. This is a result of generated nanometric substitutional defects, increasing the pinning in both cases. The non‐magnetic, low valence Ca2+ substitution increases the carriers and leads to small overdoping, while the magnetic (Pr3+) substitution only slightly deteriorates decoupling current. At high concentrations (x = 0.20, y = 0 and x = 0, y = 0.25) Jintra,c, decreases in comparison with the non‐substituted sample due to decoupling current suppression in ...