Synthesis and Sintering of Novel High-Entropy Barium Cerates Designed Through the Cluster-Plus-Glue Atom Model

This work presents the design and synthesis of novel high-entropy perovskite oxides (HEPOs) derived from BaCeO3, formulated using the cluster-plus-glue atom model. Particularly, through a carbonate-based co-precipitation technique, we synthesized three novel high-entropy perovskite oxides (HEPOs) derived from barium cerate by substituting cerium with different combinations of five different elements (Ce, Zr, Yb, Sm, La, Gd, Nd) in equal molar ratios, i.e., Ba(Ce0.2Zr0.2Yb0.2La0.2Sm0.2)O2.7, Ba(Ce0.2Sm0.2Yb0.2Nd0.2Gd0.2)O2.6, and Ba(Ce0.2Zr0.2Nd0.2La0.2Sm0.2)O2.7. Upon calcination of the as-synthesized samples at different temperatures and subsequent quenching, the formation of an entropy-stabilized single phase was analyzed and assessed. To rationalize the observed differences in phase evolution, a novel set of empirical descriptors, including configurational entropy, Goldschmidt tolerance factor, and B-site size mismatch, was proposed and discussed. With the aim of studying the sinterability of the single-phase samples, the calcination treatment was optimized by reducing its temperature and duration (i.e., 1300 °C for 6 h) so that subsequent densification higher than 95% was achieved by sintering at 1500 °C for 6 h.