Chemical stability and regulatory mechanism of multi-component HEG

High-entropy garnet (HEG) ceramics are emerging as promising matrices for nuclear waste immobilization, owing to their excellent chemical durability and structural stability. In this work, three HEG compositions with the formula A 3 Fe 5 O 12 -where A represents different combinations of rare-earth cations (A = (Y, Gd, Eu, Sm, Dy, Ho, Er, Tm), (Y, Gd, Eu, Sm, Nd, La, Dy, Ho, Er, Tm) and (Y, Gd, Eu, Sm, Nd, La, Dy, Ho, Er, Tm, Yb, Lu)) were synthesized via SPS. Their chemical durability was systematically evaluated through static and semi-dynamic leaching tests in deionized water at 90 °C. Among the three compositions, (Y, Gd, Eu, Sm, Dy, Ho, Er, Tm) 3 Fe 5 O 12 exhibited the lowest normalized elemental leaching rate, ranging from 10 -7 g∙m -2 ∙d -1 to 10 -8 g∙m -2 ∙d -1 , and the lowest long-term average cation release rate of 0.003 mg/(m 2 d). A key mechanistic insight was revealed through correlation analysis: the release rate of A-site cations shows a strong positive correlation with the degree of ionic size disorder. Furthermore, regression modeling indicates that the long-term elemental release behavior of HEGs can be effectively predicted by two structural descriptors:ionic size disorder and structural symmetry rather than by configurational entropy alone. These findings provide a concrete, property-driven design principle for developing highly durable HEG waste forms with tailorable leaching resistance.