Isostructural phase transition in hexagonal Ce1–xYxPdAl compounds

The Ce PdAl pseudoternaries belong to the ternary RTX compounds (where R stands for rare-earth, T for transition metal, X for a p-metal). We have studied three compounds with compositions x = 0.2, 0.5, and 0.8 by means of X-ray diffraction at room temperature. Moreover, Ce Y PdAl was also studied in the temperature range from 70 K to 500 K. The existence of a gap of forbidden values of the c/a ratio was confirmed. The compounds with x = 0.2 and 0.8 have different phases. The compound with x = 0.5 exhibits coexistence of both the x = 0.2 and x = 0.8 phases. The diffraction patterns and the calculated lattice parameters indicate that the Ce Y PdAl sample undergoes a phase transition towards the single-phased state at both high and low temperatures.