Superconducting properties of the lithium-substituted YBa₂Cu₄O₈ prepared by the sol-gel method

The effects of the lithium substitution for copper on the properties of the superconducting YBa₂Cu₄O₈ were studied. Single-phase YBa₂Cu_4-xLi_xO₈ was successfully prepared by the sol-gel method under ambient pressure over a composition range of 0 ≤ x ≤ 0.08, while impurity phases appeared at x=0.10 and 0.20. The lattice constants of YBa₂Cu_4-xLi_xO₈ were almost invariant with increasing lithium content x. The superconducting transition temperature decreased monotonically with increasing x in the range, 0 ≤ x ≤ 0.08. The suppression of superconductivity was discussed in terms of the impurity effect in the CuO₂ planes.