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Eighteen different 5-component equimolar rare earth zirconates were successfully synthesized by solid state reaction method. Among them, 5 of them exhibit a high-entropy fluorite structure, 8 have a high-entropy pyrochlore structure, and the remaining 5 have dual-phase structures of both pyrochlore and fluorite. For high-entropy rare earth zirconates with single-phase structure, the lattice parameter is almost linearly correlated with the average cation radius ratio. In combination with a large number of previous reports, a summary is made to study the synergistic effects of the average cation radius ratio, configuration entropy and size disorder on the single-phase formation ability of multi-component rare earth zirconates. The conclusion verifies that the size disorder of about 5% is the boundary for the multi-component rare earth zirconates to form a single-phase or dual-phase region, while the average cation radius ratio of 1.467 is the demarcation between a pyrochlore and a defective fluorite structure in the single-phase zone, and the configuration entropy had less effect. Excessive size disorder leads to the enrichment or barrenness of certain components, which is the main reason for the formation of dual phase ceramics. • 18 Different equimolar 5-component rare earth zirconates have been prepared. • The size disorder (δ *) can predict the single-phase formation ability of zirconates. • δ * = 5% is the boundary between the single- and dual-phase rare earth zirconates. • The single-phase forming ability of rare-earth zirconates is independent of entropy. [ABSTRACT FROM AUTHOR]

• Five kinds of pyrochlore high-entropy rare-earth zirconates have been prepared. • High-entropy strategy improves the electrical conductivity of rare-earth zirconate. • (Nd 0.2 Eu 0.2 Sm 0.2 Gd 0.2 Dy 0.2) 2 Zr 2 O 7 has a conductivity of 7.1 × 10–3 S·cm–1 at 1073 K. • Higher mobile vacancy concentrations, lower activation energy and the preferential O-ion migration pathway result the enhanced ion conductivity. In the present work, a series of new high-entropy rare-earth zirconates were prepared by a solid state reaction method. The crystal structure, microstructure and electrical properties of high-entropy rare-earth zirconates were characterized by means of X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and electrochemical impedance spectroscopy. All the high-entropy rare-earth zirconates have a single-phase pyrochlore structure with a relative density of more than 95.7%. The grain sizes of high-entropy rare-earth zirconates are 1.3–2.4 µm, which are finer than low-entropy rare-earth zirconates prepared by the same process. (Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 Dy 0.2) 2 Zr 2 O 7 has the excellent electrical conductivity of 7.1 × 10–3 S·cm–1 at 1073 K. [ABSTRACT FROM AUTHOR]