Structural and dynamic studies of Pr(11BH4)3. (13th September 2021)

• Record Type: Journal Article
• Authors: Gigante, Angelina; Payandeh, Seyedhosein; Grinderslev, Jakob B.; Heere, Michael; Embs, Jan Peter; Jensen, Torben R.; Burankova, Tatsiana; Remhof, Arndt; Hagemann, Hans
• Is Part Of: International journal of hydrogen energy. Volume 46:Number 63(2021)
• Page Start: 32126
• Page End: 32134
• Publication Date: 2021-09-13
• Subjects: Negative thermal expansion -- Rare earth borohydrides -- SR-PXD -- QENS -- Vibrational spectroscopy; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2021.06.232
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Rare earth borohydrides RE (BH4 )3 are studied in the context of energy storage, luminescence and magnetic applications. We have investigated the structural behavior of praseodymium borohydride Pr ( 11 BH4 )3 containing 11 B isotope because of the previously reported negative thermal expansion. Differential scanning calorimetry (DSC), in-situ variable temperature synchrotron radiation powder X-ray diffraction (SR-PXD) and infrared studies reveal that Pr ( 11 BH4 )3 undergoes to a volume contraction during the phase transition from alpha α-Pr ( 11 BH4 )3 to rhombohedral r-Pr ( 11 BH4 )3 phase upon heating to 493 K. Surprisingly, the phase transition persists upon cooling at room temperature. Vibrational analysis also shows that the stretching frequency of BH4 − anion does not change upon heating which indicates that the B–H bond length remains constant during the structural phase transition from α-Pr ( 11 BH4 )3 to r-Pr ( 11 BH4 )3 phase. Additionally, the energy barrier of reorientation motion of the BH4 − anion in the α-phase was estimated to be ca 23 kJ/mol by quasi-elastic neutron scattering (QENS) and Raman spectroscopy. Graphical abstract: Image 1 Highlights: SR-XRD confirms volume contraction at the α-Pr ( 11 BH4 )3 to r-Pr ( 11 BH4 )3 phase transition. Vibrational spectra confirm that B–H bond length do not change at this phase transition. QENS experiments give the activation energy for BH4 reorientation.