Fe‐site occupancy and superconductivity in Y_1−zCa_zBa₂(Cu_1−xFe_x)₃O_6+y Available to Purchase

X‐ray diffraction and ⁵⁷Fe Mössbauer spectroscopy studies show that partial substitution of Ca for Y in Y_1−zCa_zBa₂(Cu_1−xFe_x)₃O_6+y (0.05≤z≤0.15, 0.003≤x≤0.20) result in increased Fe solubility and a larger percentage of Fe occupancy of the Cu(2) plane site (prepared conventionally). Materials with z≳0.00 have a slightly depressed superconducting transition onset temperature T_c relative to the z=0.00 compounds. It is also shown that Fe occupancy of the Cu(2) site in Y_1−zCa_zBa₂(Cu_1−xFe_x)₃O_6+y can be substantially increased when these materials are treated at high temperatures in inert atmospheres followed by oxygenation at low temperatures. T_c decreases more rapidly in these latter materials compared to the conventionally prepared ones. Implications concerning ordered Fe‐cluster formation and superconducting pair breaking in the Cu(2) site are drawn.