Fabrication and characterization of high entropy pyrochlore ceramics

High-entropy rare-earth (RE) zirconates with pyrochlore structure were successfully fab-ricated by pressureless and spark plasma sintering. RE2Zr2O7 compound with nominal composition (La0.2Y0.2Gd0.2Nd0.2Sm0.2)Zr2O7 was prepared by simple glycine nitrate pro-cedure (GNP). GNP process yielded powders with low crystallinity and after subsequent calcination, well crystalline ceramics were formed. During calcination defective fluorite (F-RE2Zr2O7) and crystal pyrochlore (Py-RE2Zr2O7) structures coexist. Formation of pure crystalline pyrochlore occurs after sintering at 1450 degrees C. High-density ceramics, free of any additives, were obtained after powders compaction and pressureless (PS), as well as field assisted sintering technique (FAST) at 1450 degrees C. Theoretical investigations of the high-entropy RE2Zr2O7 pyrochlore systems were performed. Unit cell parameter of the obtained Py-RE2Zr2O7 is 10.5892(2) Aand 10.5999(2) A for PS and FAST sintering, respectively, which is in good agreement with the results of Density Functional Theory (DFT) calculations. The ther-mal diffusivity of sintered samples at room temperature was similar to 0.7 mm2/s for both sintering methods.(c) 2021 SECV. Published by Elsevier Espa n similar to a, S.L.U. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

High-entropy rare-earth zirconates were successfully fabricated through pressureless and spark plasma sintering. Crystalline ceramics were obtained after glycine nitrate procedure and subsequent calcination. The coexistence of defective fluorite and crystal pyrochlore structures was observed during calcination, but pure crystalline pyrochlore formed after sintering at 1450 degrees C.