Phase relationships of the R-Al-Si systems: The Pr-Al-Si isothermal section at 500 °c

In the framework of a systematic investigation of intermetallic systems, constituted by aluminium and silicon with a rare earth metal, the isothermal section at 500 °C of the Pr-Al-Si system has been experimentally investigated. The experimental techniques used were scanning electron microscopy, electron microprobe analysis and X-ray powder diffraction, and some samples have been analysed by differential thermal analysis. The existence of six ternary compounds has been confirmed, one of them showing a composition homogeneity range: τ1 PrAl2Si2 (hP5-Ce2SO2 type), τ2 Pr3Al4Si6 (hP13-Ce3Al4Si6 type), τ3 PrAlSi2 (hP8-CeAlSi2 type), τ4 Pr2Al3Si (hP3-AlB2 type), τ5 PrAl(1-x)Si(1+x) (tI12-αThSi2Si type) and τ6 Pr2AlSi (oS8-CrB type). A few compounds pertaining to the binary boundary systems Pr-Al and Pr-Si dissolve the third element