A correlation between the T c and hole concentration of La 3Ca xBa 4−xCu 7O y superconductors

Abstract

A series of samples with nominal compositions of La 3Ca xBa 4−xCu 7O y,(0 ≤ x ≤ 4.00) was prepared by the solid state reaction method. Single phase materials were obtained for 0 ≤ x ≤ 1.25 samples which had an oxygen stoichiometry, 16.021 ≤ y ≤ 16.587, equivalent to 6.866 ≤ z ≤ 7.109 per unit cell with a formula of La 1.29Ca 0.43xBa 1.71−0.43xCu 3O z. An evidence of the hole doping was observed by substituting Ca ions for Ba ions. It was interesting that increasing the Ca substitution accompanied an increase in the oxygen stoichiometry to a maximum value of 7.109 with a hole concentration of 0.311 for x = 1.00 sample. A correlation between the T c and the hole concentration was plotted and the result was very similar to that found in the YBa 2Cu 3O 7−x superconductor.