Effect of LiF addition on the formation of the superconducting YBa ₂Cu₄O₈ phase

Several possible flux materials have been investigated for preparing the superconducting YBa₂Cu₄O₈ phase under 1 atm of oxygen. LiF was a promising flux and the YBa₂Cu₄O ₈ phase was successfully obtained at 815°C with 0.5-1.0 wt.% LiF. Large amounts of LiF (>1.0wt.%) accelerated the formation of side products, i.e. BaCuO₂ and Y₂BaCuO₅, instead of the superconducting phase. LiF was also used as a flux in the syntheses of the superconducting Y_0.9Ca_0.1Ba₂Cu ₄O₈ and EuBa₂Cu₄O₈ phases, and synthesis conditions for these compounds were optimized.