Preparation and phase evolution of high-entropy oxides A2B2O7 with multiple elements at A and B sites

In this study, 37 kinds of high-entropy pyrochlore/fluorite ceramics with equiatomic multicomponent compositions were successfully synthesized and the process of phase transformation was also investigated. Eventually, the experimental results show that 33 among the high-entropy compounds exhibit a single pyrochlore/fluorite structure with all cations randomly and uniformly distributed at A and B sites. Meanwhile, the ionic radii, valence, and size disorder may be the main driving forces for the formation of single-phase high-entropy pyrochlore/fluorite oxides. Furtherly, the average radius ratio(rA/rB) is the main factor of the pyrochlore/fluorite phase transformation. And when the average radius ratio(rA/rB) extends from 1.46 to 1.78, the high-entropy pyrochlore structure is stable. When the average radius ratio rA/rB is less than 1.46, it transforms into the defective fluorite structure. This study not only further expands the high-entropy pyrochlore family and but also is expected to guide the design of high-entropy pyrochlore through composition customization.