High-entropy fluorite oxides. Issue 10 (August 2018)

• Record Type: Journal Article
• Authors: Gild, Joshua; Samiee, Mojtaba; Braun, Jeffrey L.; Harrington, Tyler; Vega, Heidy; Hopkins, Patrick E.; Vecchio, Kenneth; Luo, Jian
• Is Part Of: Journal of the European Ceramic Society. Volume 38:Issue 10(2018)
• Page Start: 3578
• Page End: 3584
• Publication Date: 2018-08
• Subjects: High-entropy ceramic -- Fluorite oxide -- Thermal conductivity -- Hardness -- Sintering; Ceramic materials -- Periodicals; Composite materials -- Periodicals; Matériaux céramiques -- Périodiques; Composites -- Périodiques; Ceramic materials; Composite materials; Periodicals; Electronic journals; 666.05
• DOI: 10.1016/j.jeurceramsoc.2018.04.010
• Languages: English
• ISSNs: 0955-2219

Abstract

Abstract: Eleven fluorite oxides with five principal cations (in addition to a four-principal-cation (Hf0.25 Zr0.25 Ce0.25 Y0.25 )O2-δ as a start point and baseline) were fabricated via high-energy ball milling, spark plasma sintering, and annealing in air. Eight of the compositions, namely (Hf0.25 Zr0.25 Ce0.25 Y0.25 )O2-δ, (Hf0.25 Zr0.25 Ce0.25 )(Y0.125 Yb0.125 )O2-δ, (Hf0.2 Zr0.2 Ce0.2 )(Y0.2 Yb0.2 )O2-δ, (Hf0.25 Zr0.25 Ce0.25 )(Y0.125 Ca0.125 )O2-δ, (Hf0.25 Zr0.25 Ce0.25 )(Y0.125 Gd0.125 )O2-δ, (Hf0.2 Zr0.2 Ce0.2 )(Y0.2 Gd0.2 )O2-δ, (Hf0.25 Zr0.25 Ce0.25 )(Yb0.125 Gd0.125 )O2-δ, and (Hf0.2 Zr0.2 Ce0.2 )(Yb0.2 Gd0.2 )O2-δ, possess single-phase solid solutions of the fluorite crystal structure with high configurational entropies (on the cation sublattices), akin to those high-entropy alloys and ceramics reported in prior studies. Most high-entropy fluorite oxides (HEFOs), except for the two containing both Yb and Gd, can be sintered to high relative densities. These single-phase HEFOs exhibit lower electrical conductivities and comparable hardness (even with higher contents of softer components such as Y2 O3 and Yb2 O3 ), in comparison with 8 mol. % Y2 O3 -stabilized ZrO2 (8YSZ). Notably, these single-phase HEFOs possess lower thermal conductivities than that of 8YSZ, presumably due to high phonon scattering by multiple cations and strained lattices.