STUDY OF STRUCTURAL DISCONTINUITY IN (Ce,Y)PdAl COMPOUNDS AT LOW AND HIGH TEMPERATURES

The Ce(1-x)Y(x)PdAl pseudoternaries belong to RTX compounds. An anomalous evolution of lattice parameters (a, c) and their ratio (c/a) was observed when varying the substitution parameter x between 0.2 < x < 0.8 at room temperature. We have studied lattice of the samples from the (Ce,Y)PdAl series in the temperature range from 8 to 1073 K. Existence of a gap of forbidden values of c/a ratio was confirmed. The compounds with x=0.,0.3 and 0.8 are single phased with values of c/a above- and below the forbidden gap, respectively, whereas the compounds with x=0.4 and 0.5 exhibit coexistence of both the phases containing c/a values belonging to the range above- and below the forbidden gap over all the range of studied temperatures. New estimation of our work leads to conclusion that the values of the gap vary in dependence on composition and temperature, what is the main difference from the RTAl and RT(1-x)T'(x)Al compounds.