Influence of composition on structural evolution of high‐entropy zirconates—cationic radius ratio and atomic size difference

Abstract

AbstractTen different high‐entropy rare‐earth zirconates with the general formula of A2Zr2O7 were synthesized using reverse coprecipitation. Thereby, five cations were mixed on the A sublattice, and their composition was varied systematically regarding cation size to vary the cationic radius ratio rA/rB and the atomic size difference δA. Phase and chemical composition as well as morphology of the synthesized materials were examined by X‐ray diffraction (XRD), scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, electron backscatter diffraction, and electron probe microanalysis. Additionally, their phase stability was investigated using high‐temperature XRD and differential scanning calorimetry. Single‐phase materials were obtained when δA was below 4.5%. This threshold value was determined and verified using additional data taken from literature. The single‐phase compositions formed pyrochlore or defect fluorite structure depending on their rA/rB with a threshold value of 1.46 being the same as for binary zirconates. Furthermore, the single‐phase compositions remained stable up to high temperatures.