TY - JOUR
T1 - Phase equilibria and metastability in the high-entropy A 6 B 2O17 oxide family with A = Zr, Hf and B = Nb, Ta
AU - Jackson Spurling, R.
AU - Skidmore, Chloe
AU - McIlwaine, Nathaniel S.
AU - Maria, Jon Paul
N1 - Funding Information:
The authors would like to acknowledge Erik Furton of Pennsylvania State University for his assistance with high-temperature X-ray diffraction data processing, as well as Saeed Almishal for his ongoing participation in discussions on the topic of complex oxide thermodynamic behavior. This material is based upon work supported by the National Science Foundation, as part of the Center for Dielectrics and Piezoelectrics under Grant Nos. IIP-1841453 and IIP-1841466. RJS was supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE1255832. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. CS and JPM acknowledge support through the Office of Naval Research Grant W911NF-16-1-0406. NSM and JPM acknowledge support from the U.S. Department of Defense through the National Defense Science and Engineering Graduate Fellowship through the Office of Naval Research, with additional support through the Office of Naval Research (Naval Research contract N00014-21-1-2515).
Publisher Copyright:
© 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
PY - 2023/4
Y1 - 2023/4
N2 - The present work details experimental phase stabilization studies for the disordered, multi-cation A6B2O17 (A = Zr, Hf; B = Nb, Ta) system. We leverage both high-temperature in situ and ex situ X-ray diffraction to assess phase equilibrium and metastability in A6B2O17 ceramics produced via reactive sintering of stoichiometric as-received powders. We observe that the A6B2O17 phase can be stabilized for any stoichiometric combination of Group 4B and 5B transition metal cations (Zr, Nb, Hf, Ta), including ternary and quinary systems. The observed minimum stabilization temperatures for these phases are generally in agreement with prior calculations for each disordered A6B2O17 ternary permutation, offering further support for the inferred cation-disordered structure and suggesting that chemical disorder in this system is thermodynamically preferable. We also note that the quinary (Zr3Hf3)(NbTa)O17 phase exhibits enhanced solubility of refractory cations which is characteristic of other high-entropy oxides. Furthermore, A6B2O17 phases experience kinetic metastability, with the orthorhombic structure remaining stable following anneals at intermediate temperatures.
AB - The present work details experimental phase stabilization studies for the disordered, multi-cation A6B2O17 (A = Zr, Hf; B = Nb, Ta) system. We leverage both high-temperature in situ and ex situ X-ray diffraction to assess phase equilibrium and metastability in A6B2O17 ceramics produced via reactive sintering of stoichiometric as-received powders. We observe that the A6B2O17 phase can be stabilized for any stoichiometric combination of Group 4B and 5B transition metal cations (Zr, Nb, Hf, Ta), including ternary and quinary systems. The observed minimum stabilization temperatures for these phases are generally in agreement with prior calculations for each disordered A6B2O17 ternary permutation, offering further support for the inferred cation-disordered structure and suggesting that chemical disorder in this system is thermodynamically preferable. We also note that the quinary (Zr3Hf3)(NbTa)O17 phase exhibits enhanced solubility of refractory cations which is characteristic of other high-entropy oxides. Furthermore, A6B2O17 phases experience kinetic metastability, with the orthorhombic structure remaining stable following anneals at intermediate temperatures.
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U2 - 10.1007/s10853-023-08396-5
DO - 10.1007/s10853-023-08396-5
M3 - Article
AN - SCOPUS:85151431427
SN - 0022-2461
VL - 58
SP - 6164
EP - 6173
JO - Journal of Materials Science
JF - Journal of Materials Science
IS - 14
ER -