O.V. Pshyk; A. Vasylenko; P. Küttel; B. Wicher; P. Schweizer; J. Michler; T.E.J. Edwards
Communications Materials (2025)
Refractory ceramic materials are critical for applications in extreme high temperature
environments. Refractory high-entropy ceramics belong to this class of materials and show great
potential due to their remarkable combination of properties. Traditionally, increasing
compositional complexity and chemical diversity of high-entropy ceramics whilst maintaining a
stable single-phase solid solution has been a primary design strategy for developing new ceramics.
Here, we unveil an alternative strategy based on deviation from conventional equimolar
composition towards non-equimolar composition space, enabling tuning the metastability level of
the supersaturated single-phase solid solution. By employing high-temperature micromechanical
testing and post-mortem microstructural characterization of refractory metal-based high-entropy
nitrides, we observed the activation of an additional strengthening mechanism upon spinodal
decomposition of the metastable phase into coherent cubic-phase domains exhibiting
compositional modulation. This process propels the yield strength of a non-equimolar nitride at
1000C to a staggering 6.9 GPa, that is 43% higher than the most robust equimolar nitride.
DOI: https://doi.org/10.1038/s43246-025-01047-z