The ternary system cerium-rhodium-silicon

Phase relations have been established in the ternary system Ce-Rh-Si for the isothermal section at 800 deg. C based on X-ray powder diffraction and EPMA on about 80 alloys, which were prepared by arc melting under argon or by powder reaction sintering. From the 25 ternary compounds observed at 800 deg. C 13 phases have been reported earlier. Based on XPD Rietveld refinements the crystal structures for 9 new ternary phases were assigned to known structure types. Structural chemistry of these compounds follows the characteristics already outlined for their prototype structures: τ7-Ce3RhSi3, (Ba3Al2Ge2-type), τ8-Ce2Rh3-xSi3+x (Ce2Rh1.35Ge4.65-type), τ10-Ce3Rh4-xSi4+x (U3Ni4Si4-type), τ11-CeRh6Si4 (LiCo6P4-type), τ13-Ce6Rh30Si19.3 (U6Co30Si19-type), τ18-Ce4Rh4Si3 (Sm4Pd4Si3-type), τ21-CeRh2Si (CeIr2Si-type), τ22-Ce2Rh3+xSi1-x (Y2Rh3Ge-type) and τ24-Ce8(Rh1-xSix)24Si (Ce8Pd24Sb-type). For τ25-Ce4(Rh1-xSix)12Si a novel bcc structure was proposed from Rietveld analysis. Detailed crystal structure data were derived for τ3-CeRhSi2 (CeNiSi2-type) and τ6-Ce2Rh3Si5 (U2Co3Si5-type) by X-ray single crystal experiments, confirming the structure types. The crystal structures of τ4-Ce22Rh22Si56, τ5-Ce20Rh27Si53 and τ23-Ce33.3Rh58.2-55.2Si8.5-11.5 are unknown. High temperature compounds with compositions Ce10Rh51Si33 (U10Co51Si33-type) and CeRhSi (LaIrSi-type) have been observed in as-cast alloys but these phases do not participate in the phase equilibria at 800 deg. C. - Graphical abstract: Phase relations in the ternary system Ce-Rh-Si have been established for the isothermal section at 800 deg. C based on X-ray powder and single-crystal diffraction, metallography, SEM and EMPA techniques on about 80 alloys. 25 ternary compounds were observed.