A series of single phase La1.5 − SrxBa1.5 − Cu3Oy(0 ≤ x ≤ 0.80) compounds with a tetragonal triple-perovskite unit-cell have been prepared by solid-state reaction. With increasing x, unit-cell a axis, volume, density, and peritectic transition temperature (Tp) of La1.5 − SrxBa1.5 − Cu3Oydecrease monotonically. The peak position of Tp measured in the 25 mL/min flowing O2 atmosphere and 10 °C/min heating rate decreases from 1105 to 1080 °C as x increases from 0 to 0.80. The oxygen atom loss in the peritectic transition is 0.38 ± 0.05 O-atom-mole−1.
