Altering the Structural Properties of A2B12H12 Compounds via Cation and Anion Modifications

Published

October 5, 2015

Author(s)

Wan Si NMN Tang, Terrence J. Udovic, Vitalie Stavila

Abstract

The recent discovery of unusually high cationic conductivity in Na₂B₁₂H₁₂ above its entropy-driven, order-disorder phase transition near 529 K and the expected similar conductivity behavior in Li₂B₁₂H₁₂ above its transition near 615 K have lead us to investigate modifications of these two materials in an effort to reduce their transition temperatures and thus extend their high conductivities to more technological favorable values. Differential scanning calorimetry measurements perhalogenated Na₂B₁₂X₁₂ (X=Cl and I), which are larger anion relatives of Na₂B₁₂H₁₂, suggest unfavorably higher transition temperature near 730 K and 816 K, respectively. New mixed-cation Li_yNa_2-yB₁₂H₁₂ phases show intermediate transition temperatures between those of Li₂B₁₂H₁₂ and Na₂B₁₂H₁₂. X-ray diffraction measurements and neutron vibrational spectra corroborate similar low-temperature ordered structures as pure Li₂B₁₂H₁₂ (for y=0.67, 1, and 1.33) with Li⁺ and Na⁺ disordered among the near-trigonal cation sites.

Citation

Journal of Alloys and Compounds

Volume

645

Pub Type

Journals

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Keywords

Borohydrides, order-disorder phase transition, superionic conductivity, ionic modification, perhalogenated dodecaborate, dodecahydro-closo-dodecaborate

Citation

NMN, W. , Udovic, T. and Stavila, V. (2015), Altering the Structural Properties of A₂B₁₂H₁₂ Compounds via Cation and Anion Modifications, Journal of Alloys and Compounds, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=917141 (Accessed December 3, 2024)