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Research Article | Open Access

21-Component compositionally complex ceramics: Discovery of ultrahigh-entropy weberite and fergusonite phases and a pyrochlore-weberite transition

Mingde QINaHeidy VEGAa,bDawei ZHANGa,cSarath ADAPAdAndrew J. WRIGHTaRenkun CHENc,dJian LUOa,c( )
Department of Nano Engineering, University of California San Diego, La Jolla 92093, USA
Department of Chemistry and Biochemistry, University of California San Diego, La Jolla 92093, USA
Program of Materials Science and Engineering, University of California San Diego, La Jolla 92093, USA
Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla 92093, USA
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Graphical Abstract


Two new high-entropy ceramics (HECs) in the weberite and fergusonite structures, along with the unexpected formation of ordered pyrochlore phases with ultrahigh-entropy compositions and an abrupt pyrochlore-weberite transition, are discovered in a 21-component oxide system. While the Gibbs phase rule allows 21 equilibrium phases, 9 out of the 13 compositions examined possess single HEC phases (with ultrahigh ideal configurational entropies: ~2.7kB per cation or higher on one sublattice in most cases). Notably, (15RE1/15)(Nb1/2Ta1/2)O4 possess a single monoclinic fergusonite (C2/c) phase, and (15RE1/15)3(Nb1/2Ta1/2)1O7 form a single orthorhombic (C2221) weberite phase, where 15RE1/15 represents Sc1/15Y1/15La1/15Pr1/15Nd1/15Sm1/15Eu1/15Gd1/15Tb1/15Dy1/15Ho1/15Er1/15Tm1/15 Yb1/15Lu1/15. Moreover, a series of eight (15RE1/15)2+x(Ti1/4Zr1/4Ce1/4Hf1/4)2-2x(Nb1/2Ta1/2)xO7 specimens all exhibit single phases, where a pyrochlore-weberite transition occurs within 0.75 < x < 0.8125. This cubic-to-orthorhombic transition does not change the temperature-dependent thermal conductivity appreciably, as the amorphous limit may have already been achieved in the ultrahigh-entropy 21-component oxides. These discoveries expand the diversity and complexity of HECs, towards many-component compositionally complex ceramics (CCCs) and ultrahigh-entropy ceramics.

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Journal of Advanced Ceramics
Pages 641-655
Cite this article:
QIN M, VEGA H, ZHANG D, et al. 21-Component compositionally complex ceramics: Discovery of ultrahigh-entropy weberite and fergusonite phases and a pyrochlore-weberite transition. Journal of Advanced Ceramics, 2022, 11(4): 641-655.








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Received: 06 January 2022
Revised: 21 January 2022
Accepted: 23 January 2022
Published: 08 March 2022
© The Author(s) 2022.

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