The development of configurational entropy formulation for high-entropy oxides: Review and outlook

Abstract

High-entropy oxides (HEOs) have garnered significant attention due to their unique ability to stabilize disordered phases through configurational entropy. In this review, we delve into both the theoretical and practical implications of configurational entropy to classify low, medium, and high entropy materials, underscoring its vital role of multiple sublattice and defects of cation and anion in influencing phase stability, structural intricacy, and functional performance. We extend our discussion to encompass the four core effects of HEMs, and non-configurational entropy contributions, namely vibrational, electronic, magnetic, entropy, and dislocation entropy, and evaluate how their collective effects shape the overall thermodynamic behavior of these materials. Advanced entropy models that incorporate multi-sublattice configurations, anion defects, and short-range order are critically evaluated, with computational simulations and machine-learned interaction potentials serving as complementary tools. Additionally, high-throughput experimental and computational explorations are highlighted as essential methods for validating these theoretical models. By examining the interplay between configurational and non-configurational entropy, this review illuminates their combined influence on the properties and performance of HEOs. Ultimately, we identify current challenges and opportunities, advocating for integrative computational and experimental strategies to broaden the compositional landscape of high-entropy materials (HEMs) and facilitate their rational design for advanced applications in energy conversion, catalysis, and high-temperature environments.