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Pr1+xBa2-xCu3O7+/-delta solid solution was investigated by means of X-ray powder diffraction and Rietveld analysis. Single-phase PrBa2Cu3O7+/-delta (Pr123) can be synthesized under a Pr-rich condition by sintering at 950 degreesC in air. The solubility of Pr1+xBa2-xCu3O7+/-delta solid solution is 0.08less than or equal tox less than or equal to0.80. The structure of Pr1+xBa2-xCu3O7+/-delta is orthorhombic for 0.08less than or equal tox<0.30, and transforms into tetragonal for 0.30less than or equal toxless than or equal to0.80. To form single-phase Pr123, the Ba sites in the Pr123 structure are partially occupied by excess Pr ions, and the smallest amount of excess Pr is x=0.08. Meanwhile, all Ba ions stay in the Ba sites. (C) 2004 International Centre for Diffraction Data.