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Pressure‐induced phase transitions in Na 2 B 12 H 12 , structural investigation on a candidate for solid‐state electrolyte
Author(s) -
Moury Romain,
Łodziana Zbigniew,
Remhof Arndt,
Duchêne Léo,
Roedern Elsa,
Gigante Angelina,
Hagemann Hans
Publication year - 2019
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520619004670
Subject(s) - bulk modulus , materials science , electrolyte , ambient pressure , thermal expansion , phase transition , thermodynamics , diffraction , fast ion conductor , ionic bonding , boron , structural stability , phase (matter) , electrochemistry , battery (electricity) , ion , chemistry , electrode , composite material , physics , organic chemistry , optics , power (physics) , structural engineering , engineering
closo ‐Borates, such as Na 2 B 12 H 12 , are an emerging class of ionic conductors that show promising chemical, electrochemical and mechanical properties as electrolytes in all‐solid‐state batteries. Motivated by theoretical predictions, high‐pressure in situ powder X‐ray diffraction on Na 2 B 12 H 12 was performed and two high‐pressure phases are discovered. The first phase transition occurs at 0.5 GPa and it is persistent to ambient pressure, whereas the second transition takes place between 5.7 and 8.1 GPa and it is fully reversible. The mechanisms of the transitions by means of group theoretical analysis are unveiled. The primary‐order parameters are identified and the stability at ambient pressure of the first polymorph is explained by density functional theory calculations. Finally, the parameters relevant to engineer and build an all‐solid‐state battery, namely, the bulk modulus and the coefficient of the thermal expansion are reported. The relatively low value of the bulk modulus for the first polymorph (14 GPa) indicates a soft material which allows accommodation of the volume change of the cathode during cycling.