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Title: Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N

An understanding of the heterostructural implications on alloying in the aluminum nitride-scandium nitride system ($${\mathrm{Al}}_{1{-}x}{\mathrm{Sc}}_{x}\mathrm{N}$$) 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 $${\mathrm{Al}}_{1{-}x}{\mathrm{Sc}}_{x}\mathrm{N}$$ 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 $${\mathrm{Al}}_{1{-}x}{\mathrm{Sc}}_{x}\mathrm{N}$$ system, suggests material design strategies for even greater property enhancements, and demonstrates the increased property tunability and underexplored nature of nonequilibrium heterostructural alloys.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [2] ;  [3] ;  [5] ;  [1] ;  [3]
  1. Colorado School of Mines, Golden, CO (United States). Metallurgical and Materials Engineering; National Renewable Energy Lab. (NREL), Golden, CO (United States)
  2. Univ. of Colorado, Boulder, CO (United States). Dept. of Chemical and Biological Engineering
  3. Colorado School of Mines, Golden, CO (United States). Metallurgical and Materials Engineering
  4. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  5. National Renewable Energy Lab. (NREL), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States). Dept. of Chemical and Biological Engineering
Publication Date:
Report Number(s):
NREL/JA-5K00-71970
Journal ID: ISSN 2475-9953
Grant/Contract Number:
AC36-08GO28308; DMREF-1534503; CBET-1433521
Type:
Published Article
Journal Name:
Physical Review Materials
Additional Journal Information:
Journal Volume: 2; Journal Issue: 6; Journal ID: ISSN 2475-9953
Publisher:
American Physical Society (APS)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; dielectric properties; elastic modulus; phase diagrams; piezoelectricity; spinodal decomposition
OSTI Identifier:
1457812
Alternate Identifier(s):
OSTI ID: 1462331

Talley, Kevin R., Millican, Samantha L., Mangum, John, Siol, Sebastian, Musgrave, Charles B., Gorman, Brian, Holder, Aaron M., Zakutayev, Andriy, and Brennecka, Geoff L.. Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N. United States: N. p., Web. doi:10.1103/PhysRevMaterials.2.063802.
Talley, Kevin R., Millican, Samantha L., Mangum, John, Siol, Sebastian, Musgrave, Charles B., Gorman, Brian, Holder, Aaron M., Zakutayev, Andriy, & Brennecka, Geoff L.. Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N. United States. doi:10.1103/PhysRevMaterials.2.063802.
Talley, Kevin R., Millican, Samantha L., Mangum, John, Siol, Sebastian, Musgrave, Charles B., Gorman, Brian, Holder, Aaron M., Zakutayev, Andriy, and Brennecka, Geoff L.. 2018. "Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N". United States. doi:10.1103/PhysRevMaterials.2.063802.
@article{osti_1457812,
title = {Implications of heterostructural alloying for enhanced piezoelectric performance of (Al,Sc)N},
author = {Talley, Kevin R. and Millican, Samantha L. and Mangum, John and Siol, Sebastian and Musgrave, Charles B. and Gorman, Brian and Holder, Aaron M. and Zakutayev, Andriy and Brennecka, Geoff L.},
abstractNote = {An understanding of the heterostructural implications on alloying in the aluminum nitride-scandium nitride system (${\mathrm{Al}}_{1{-}x}{\mathrm{Sc}}_{x}\mathrm{N}$) 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 ${\mathrm{Al}}_{1{-}x}{\mathrm{Sc}}_{x}\mathrm{N}$ 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 ${\mathrm{Al}}_{1{-}x}{\mathrm{Sc}}_{x}\mathrm{N}$ system, suggests material design strategies for even greater property enhancements, and demonstrates the increased property tunability and underexplored nature of nonequilibrium heterostructural alloys.},
doi = {10.1103/PhysRevMaterials.2.063802},
journal = {Physical Review Materials},
number = 6,
volume = 2,
place = {United States},
year = {2018},
month = {6}
}

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