Synthesis and Characterization of High-Entropy A2B2O7 Pyrochlore with Multiple Elements at A and B Sites.

Single nano high-entropy pyrochlore-type compound (A₂B₂O₇) with 7 different rareearth cations at site A and 3 different metal cations at site B with equiatomic amounts (7A_1/7)₂(3B_1/3)₂O₇ is successfully obtained. The powder with nominal composition (La_1/7Sm_1/7Nd_1/7Pr_1/7Y_1/7Gd_1/7Yb_1/7)₂(Sn_1/3Hf_1/3Zr_1/3)₂O₇ was fabricated by reacting metal nitrates (site A) and metal chlorides (site B) with glycine during the combustion reaction. The XRD analysis revealed that the powder attained during synthesis is in an amorphous state. To induce crystallization of the obtained pyrochlore structure, the post-calcination process at 600-1500 oC was conducted and studied. Results of this study showed that the monophase pyrochlore (A₂B₂O₇) structure is obtained during the calcination at 900 °C. The high-density ceramic pellet with 97% of theoretical density and free of any additives was obtained through pressureless sintering at 1650 °C for 4 h in the air using the powder calcined at 900 °C. [ABSTRACT FROM AUTHOR]