Interaction of Components and Crystal Structure of Compounds in the Pr–Cu–Ge System.

Using X-ray diffraction phase and structural analysis and partially microstructural analysis methods the phase equilibria in the ternary system Pr–Cu–Ge were investigated and the isothermal sections of the phase diagram of the system at 870 K (0–50 at.% of Pr) and 670 K (50–100 at.% of Pr) were constructed. The existence of seven ternary compounds PrCu2Ge2, Pr2CuGe6, Pr2Cu3Ge3, PrCu0.817Ge2, Pr6Cu8Ge8, PrCu1.25–0.95Ge0.75–1.05, PrCu0.77–0.5Ge1.23–1.5 was established at 870 K. Only one ternary germanide ~ Pr0.6Cu0.22Ge0.18 with undetermined crystal structure was found in R rich range at 670 K. All ternary germanides are formed at constant composition except phases with AlB2 structure type. Appreciable solubility of the third component in the compounds of binary systems was not observed. The structure parameters were determined for ternary germanides: Pr2CuGe6 (structure type (ST) Ce2CuGe6, Pearson symbol (PS) oS18, space group (SG) Amm2, a = 4.19300(4) Å, b = 4.05742(4) Å, c = 21.4823(2) Å, RI = 0.0686, RP = 0.0993), PrCu1.25Ge0.75 (ST AlB2, PS hP3, SG P6/mmm, a = 4.2922(2) Å, c = 3.9193(3) Å, RI = 0.0543, RP = 0.1036), PrCu0.72Ge1.28 (ST AlB2, PS hP3, SG P6/mmm, a = 4.19347(6) Å, c = 4.1817(1) Å, RI = 0.0504, RP = 0.0728). Relationships of investigated system Pr–Cu–Ge with previously studied R–Cu–Ge systems, and structure peculiarities of established ternary germanides of Cu and Pr were analyzed. [ABSTRACT FROM AUTHOR]