Multi-element entropy stabilized layered diboride solid solutions with tunable thermal expansion

Principal Investigator: Frederic Monteverde

Involved personnel: Federico Saraga

Starting date: 01/06/2021
Duration: 6 months
Call: Proposal nr. 20210215 – MCX beamline at Elettra – Sincrotrone Trieste S.C.p.A
Project Coordinator: Frederic Monteverde
Consortium: CNR-ISTEC, Materials Science and Engineering Department Missouri Science and Technology University, Elettra – Sincrotrone Trieste S.C.p.A

Entropy stabilized (ES) ultra-high temperature ceramics are complex, multi-element, solid solutions of the IV-V-VI transition metal groups and cover a crucial place in future energy and extreme environment applications. Among them, layered diboride solid solutions can incorporate up to five and even more transition metals such as Ti, Nb, Zr, Hf, Ta, W, and Mo in an AlB2-type hexagonal lattice presenting higher performance than their parent boride mixtures. These materials offer opportunities to tailor new functional properties which are beyond the rule of mixture and strongly depend on their structure and chemical environment. Following our recent finding that different transition metals occupying the same crystallographic sites can trigger an anisotropic thermal expansion response, with this proposal we aim to investigate, for the first time, the range of tunability of the thermal expansion upon metals replacement. To achieve such goal we have selected three series of metal layered diborides, namely: (Ti-Zr-Hf-Mo-Me1)B2, (Ti-Zr-Hf-Mo-Me1-Me2)B2, and (Ti-Zr-Hf-Mo-Me1-Me2-Me3)B2 with MeX the extra metals selected among Nb, W, and Ta. At the same time these measurements will complement the recent EXAFS experiment (i.e. see Exp. Report 20200101).

Publications & Patents:

  • F.Monteverde, F. Saraga, M. Gaboardi, Compositional disorder and sintering of entropy stabilized (Hf,Nb,Ta,Ti,Zr)B2 solid solution powders,
  • F.Monteverde, F. Saraga, Entropy stabilized single-phase (Hf,Nb,Ta,Ti,Zr)B2 solid solution powders obtained via carbo/boro-thermal reduction,