Preparation and Properties of High-Entropy Pyrochlore A2Ti2O7 with Multi-Elements at A Site

High-entropy pyrochlore is expected to be a solidified polynucleotide waste matrix with excellent properties. To investigate the underlying mechanism or key factors governing their physical and chemical properties, we synthesized A2Ti2O7 (A represents a rare earth element: a combination of Gd, Dy, Ho, Er, Yb and Nd) series ceramics via conventional sintering method, and characterized their structure and properties. The X-ray diffraction and Raman spectroscopy analysis of the samples show that the prepared multi-component ceramics are all in single-phase structure of pyrochlore. The solution of multiple elements causes a lattice distortion effect. The density and hardness of high-entropy ceramics are higher than those of low- and medium-entropy ceramics. High-entropy ceramics have the lowest thermal conductivity as well. The measured thermal conductivity exhibits a strong negative correlation with the mixing entropy of A-site cations and a weak negative correlation with size disorder. Therefore, the mixing entropy is a reliable indicator for predicting the thermal conductivity of multi-component pyrochlore solid solution ceramics. Compared with low-entropy pyrochlore, high-entropy pyrochlore exhibits superior performance, indicating that it possesses potential advantages as a solidified waste matrix.