Increasing theT_cof YBa₂Cu₄O₈to 90 K by Sr substitution via the KOH flux method

Abstract

Sr-substituted YBa 2 Cu 4 O 8 (Y124) crystals synthesized from a KOH solution at a low temperature exhibited a dramatic increase in the superconducting transition temperature (T c ) to approximately 90 K with the increasing Sr content. The c-lattice parameter increased slightly when the amount of Sr in the KOH solution was little, and then gradually decreased as the Sr content increased. From the viewpoint of the hole-doping mechanism and ionic radius, the unexpected T c increase is attributed to the substitution of the Y site with Sr, while the decrease in the c-lattice parameter is attributed to the Sr substituting for Ba.