Doping-Induced Polyamorphic Transitions in Fluorite Oxides

Fluorite oxides, such as HfO_{2}, exhibit rich and tunable phase behaviors, making them promising candidates for next-generation electronic devices. In this field, a key challenge consists in the design of amorphous HfO_{2}-based high-k materials with both structural and performance stability. Here, using molecular dynamics simulations supported by experimental measurements, we reveal that Ba doping stimulates a polyamorphic transition in HfO_{2}, yielding a semiordered amorphous phase characterized by amorphized oxygens embedded within an ordered metal sublattice. We find that this phase arises from degenerate short-range symmetry breaking modes, consistent with Pauling's parsimony rule. Notably, the semiordered amorphous structure is thermodynamically stable and displays a wider bandgap and higher dielectric constant than the conventional continuous-random-network amorphous structure, owing to suppressed subgap states and increased Born effective charges. We further demonstrate that this structural motif generalizes to Ba-, Sr-, and Ca-doped HfO_{2} and ZrO_{2}, establishing a broadly applicable strategy for designing high-performance amorphous dielectrics.