Volume 51, Issue 5 pp. 1445-1454
research papers

Nanodomains and local structure in ternary alkaline-earth hexaborides

Robert Koch

Corresponding Author

Robert Koch

Kazuo Inamori School of Engineering, Alfred University, 2 Pine Street, Alfred, NY14802, USA

Robert Koch, e-mail: [email protected]Search for more papers by this author
Peter C. Metz

Peter C. Metz

Kazuo Inamori School of Engineering, Alfred University, 2 Pine Street, Alfred, NY14802, USA

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Oscar Jaime

Oscar Jaime

Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive – MC 0411, La Jolla, CA92093, USA

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C. Ingram Vargas-Consuelos

C. Ingram Vargas-Consuelos

Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive – MC 0411, La Jolla, CA92093, USA

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Raúl Borja-Urby

Raúl Borja-Urby

Centro de Nanociencias y Micro y Nanotecnologías, Instituto Politécnico Nacional, Avenida Luis Enrique Erro S/N, C.P. 07738, Ciudad de México, Mexico

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J. Y. Peter Ko

J. Y. Peter Ko

Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY14583, USA

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James T. Cahill

James T. Cahill

Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive – MC 0411, La Jolla, CA92093, USA

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Doreen Edwards

Doreen Edwards

Kate Gleason College of Engineering, Rochester Institute of Technology, 77 Lomb Memorial Drive, Rochester, NY14623, USA

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Victor R. Vasquez

Victor R. Vasquez

Chemical and Materials Engineering Department, University of Nevada, 1664 North Virginia Street – MS 388, Reno, NV89557, USA

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Olivia A. Graeve

Olivia A. Graeve

Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive – MC 0411, La Jolla, CA92093, USA

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Scott T. Misture

Scott T. Misture

Kazuo Inamori School of Engineering, Alfred University, 2 Pine Street, Alfred, NY14802, USA

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First published: 24 September 2018

Abstract

The local structures of ternary alkaline-earth hexaborides (MB6, M = Ca0.5Sr0.5, Ca0.5Ba0.5 and Sr0.5Ba0.5) have been analysed using X-ray pair distribution function (PDF) analysis, Raman spectroscopy and transmission electron microscopy (TEM). The results show significant local deviations from the average cubic structure within the boron sub-lattice and support the conclusion that rapid synthesis processes lead to the formation of coherent nanodomains over length scales of about 10 nm. Reverse Monte Carlo fitting of the PDFs allows for quantification of the displacement disorder within the boron sub-lattice as a function of sample composition. Detailed Raman spectroscopy studies and high-resolution TEM support the models derived from X-ray scattering. The average magnitude of the static displacement disorder varies by sample composition and positively correlates with the cation radius ratios across the three compositions. The new models form a foundation for future computational and experimental studies aimed at understanding and predicting properties of hexaborides.

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