Thermodynamic Ground States of Multifunctional Metal Dodecaborides
- Donghua Univ., Shanghai (China)
- Southern Univ. of Science and Technology, Guangdong (China)
- Technische Univ. Darmstadt (Germany)
A large class of metal dodecaborides (MB12) is currently raising great expectations as multifunctional materials, but their refined structures are not fully resolved, which severely limits the understanding of structure–property relationships. In this paper, we report that the tetragonal tI26 structure is the thermodynamic ground state of ScB12, and we predict the tetragonal YB12, ZrB12, and HfB12 to be metastable, whereas the cubic cF52 structure is the high-temperature phase of ScB12 and represents the thermodynamic ground state of YB12, ZrB12, and HfB12. Crystal structures based on experimental synchrotron data are reported for tetragonal ScB12 and cubic YB12, and high-temperature X-ray data prove the phase transformation into cubic ScB12. In both types of crystal structures, the most prominent feature is that the boron atoms are linked into a rigid three-dimensional network of interconnected, empty B12-cuboctahedra with metal atoms in large cages in form truncated octahedra consisting of 24 boron atoms. It is the uniqueness of these configurations that causes unusual functionalities, i.e., the coexistence of high hardness, low density, and good electrical conductivity. Furthermore, we elucidate that these physical properties are of electronic origins. These findings not only resolve the longstanding structural puzzle of this family of MB12 but also provide crucial insights into the underlying nature of their remarkable properties.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
- Sponsoring Organization:
- National Natural Science Foundation of China (NSFC)
- OSTI ID:
- 1495449
- Journal Information:
- Chemistry of Materials, Vol. 31, Issue 3; ISSN 0897-4756
- Publisher:
- American Chemical Society (ACS)Copyright Statement
- Country of Publication:
- United States
- Language:
- ENGLISH
Web of Science
Radial X‐Ray Diffraction Study of Superhard Early Transition Metal Dodecaborides under High Pressure
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journal | April 2019 |
Enhancing the Vickers hardness, melting point and thermodynamic properties of hafnium dodecaboride
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journal | January 2019 |
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