Synthesis of bulk superconductors RBa 2Cu 4O 8 (R = Tm, Er, Ho, Y, Dy and Gd) by a simple solid-state reaction method

Abstract

Bulk superconductors of RBa 2Cu 4O 8 (R = Tm, Er, Ho, Y, Dy and Gd) were successfully synthesized at 1 atm oxygen pressure. The mixed starting powders (R 2O 3, BaCO 3 and CuO) were pressed and pre-sintered at 900°C for 2 days in air or at 800°C for 12 h in vacuo, and then annealed in oxygen flow at the rate of 200 cm 3/min. Lattice constants increased and T c values decreased with increasing ionic radii of rare earth elements for the R-substituted RBa 2Cu 4O 8 system. In the case of R = Yb and Sm, the RBa 2Cu 4O 8 phase was not obtained in our experiments.