Pr and Ca co-doping effects on the flux pinning properties in (Y1-x-yPrxCay)Ba2Cu3O7-δ

The effects of Pr and Ca co-doping on the critical current density J(c) and the critical temperature T-c in (Y1-x-yPrxCay)Ba2Cu3O7-delta have been investigated. Though Ca doping is expected to supply mobile holes to the CuO2 plane, the T, decreases monotonically with increasing Ca concentration (y), regardless of Pr concentration (x). When the x is x less than or equal to 0.05, the variation in J(c)-H curves with increasing y is slight and the J(c) decreases monotonically in accordance with the decrease in T-c. In contrast, when the x is high (x = 0.10), a remarkable enhancement of a shoulder feature in J(c)-H curves with increasing y is observed. The enhancement results in significant increase in J(c) under magnetic fields. We conclude that the enhancement of the "shoulder" relates to the partial substitution of Pr ions for Ba sites, which is facilitated by the additional Ca doping. (C) 2002 Elsevier Science B.V. All rights reserved.