Thermal properties of polycrystalline [Mn(NH3)6](ClO4)2
| Autor: | Łukasz Hetmańczyk, Anna Migdał-Mikuli, Joanna Hetmańczyk, Edward Mikuli |
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| Rok vydání: | 2014 |
| Předmět: |
Phase transition
Chemistry hexaamminemanganese(II) perchlorate Analytical chemistry Crystal structure X-ray powder diffraction (XRPD) Condensed Matter Physics Spectral line DSc FT-IR Crystallography phase transition Thermal Molecule Crystallite Physical and Theoretical Chemistry Fourier transform infrared spectroscopy thermal decomposition (TG/DTG/QMS) Powder diffraction |
| Zdroj: | Journal of Thermal Analysis and Calorimetry. 118:1049-1056 |
| ISSN: | 1588-2926 1388-6150 |
| DOI: | 10.1007/s10973-014-3803-6 |
| Popis: | The X-ray powder diffraction (XRPD) pattern of [Mn(NH 3 ) 6 ](ClO 4 ) 2 at room temperature can be indexed in the regular (cubic) system (Fm 3m space group) with lattice cell parameter a = 11.5729 A ̊ and with four mole- cules per unit cell. The XRPD pattern at 100 K is evidently different, and it indicates lowering of the crystal structure. One phase transition at T h C1 = 143.5 K (on heating) and at T c C1 = 137.6 K (on cooling) was detected by DSC for [Mn(NH 3 ) 6 ](ClO 4 ) 2 in the range of 120–300 K. The fol- lowing thermodynamic parameters for phase I $ phase II transition were obtained: D H = 3.1 ± 0.2 kJ mol - 1 and D S = 21.6 ± 0.3 J mol - 1 K - 1 . The large value of entropy changes ( D S ) indicates considerable configurational disor- der in the high temperature phase. The presence of 5.9 K hysteresis of the phase transition temperature at T C and sharpness of the heat flow anomaly attest that the detected phase transition is of the first-order type. Appearing of the two new bands (splitting of d s (HNH) F 1u mode) in FT-MIR spectra at the vicinity of 1200 cm - 1 suggests that the phase transition undergoes a change of the crystal structure. |
| Databáze: | OpenAIRE |
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