Year: 2026
Type: preprint
Abstract: The development of high-entropy ceramics (HECs) over the past decade has extended the exploration to a diverse range of oxides, borides, silicides, carbides, nitrides, fluorides, and other ceramic solid solutions, encompassing an increasingly broad range of crystal structures and bonding characteristics and exhibiting promising mechanical, thermal, and functional properties. Initial studies predominantly focused on five-component equimolar compositions. In 2020, we proposed extending the exploration beyond HECs to the broader class of "compositionally complex ceramics" (CCCs), in which rational non-equimolar compositional designs and long- and short-range order can reduce configurational entropy while providing additional opportunities to tailor and enhance materials properties, with the goal of outperforming their higher-entropy counterparts. Because CCCs have been defined somewhat vaguely in previous publications, this review seeks to establish more rigorous and explicit criteria for defining CCCs, despite the unavoidable degree of arbitrariness in the choice of thresholds. Meanwhile, 10-21-component ultrahigh-entropy ceramics have emerged as a subset of HECs, exhibiting intriguing abrupt phase transitions. Dual-phase CCCs have also been reported, with thermodynamic equilibria governing cation partitioning between the two phases. Recent studies have further revealed that grain-boundary complexion (phase-like) transitions can occur in CCCs, influencing microstructural evolution and materials properties. Overall, CCCs provide a versatile platform for tailoring materials properties through the interplay of diverse crystal structures and bonding characteristics, compositional complexity, rational non-equimolar designs, long- and short-range order, defects, and microstructural and interfacial engineering.
Source: arXiv (Cornell University)
Author: Luo, Jian
Institution: University of California San Diego
Language: English
Topic: High Entropy Alloys Studies
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204746762