期刊
PHYSICAL REVIEW MATERIALS
卷 2, 期 6, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevMaterials.2.063802
关键词
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资金
- U.S. National Science Foundation [DMREF-1534503]
- U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, as part of the Energy Frontier Research Center, Center for Next Generation of Materials by Design: Incorporating Metastability [DE-AC36-08GO28308]
- National Science Foundation [CBET-1433521]
- U.S. Department of Energy Graduate Assistance in Areas of National Need (GAANN) program [P200A150156S]
- U.S. Department of Energy's Office of Energy Efficiency and Renewable Energy, located at NREL
- Div Of Chem, Bioeng, Env, & Transp Sys [1433521] Funding Source: National Science Foundation
An understanding of the heterostructural implications on alloying in the aluminum nitride-scandium nitride system (Al1-xScxN) can highlight opportunities and design principles for enhancing desired material properties by leveraging nonequilibrium states. The fundamental thermodynamics, and therefore composition-and structure-dependent mechanisms, underlying property evolution in this system have not been fully described, despite significant recent efforts driven by interest in enhanced piezoelectric performance. Practical realization of these enhanced properties, however, is hindered by the strong driving thermodynamic driving force for phase separation in the system, highlighting the need for increased study into the role of heterostructural alloying on the thermodynamics and composition-structure-property relationships in this system. With this need in mind, ab initio computed alloy thermodynamics and properties are compared to combinatorial thin-film synthesis and characterization to develop a more complete picture of the structure and property evolution across the Al1-xScxN composition space. The combination of structural frustration and a flattened free-energy landscape lead to substantial increases in electromechanical response. The energy scale of alloy metastability is found to be much larger than previously reported, helping to explain difficulties in achieving homogeneous materials with high scandium concentration. Scandium substitution for aluminum softens the wurtzite crystal lattice, and energetic proximity to the competing hexagonal boron-nitride structure enhances the piezoelectric stress coefficient. Overall, this work provides insight into the understanding of the structure-processing-property relationships in the Al1-xScxN system, suggests material design strategies for even greater property enhancements, and demonstrates the increased property tunability and underexplored nature of nonequilibrium heterostructural alloys.
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