Crystal structure, phase transitions and ferroelastic properties of [(CH3)2NH2]3[Bi2Cl9] |
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| Authors: | M Wojta? R Jakubas J Zaleski J Baran |
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| Institution: | a Faculty of Chemistry, University of Wroc?aw, Joliot-Curie 14, 50-383 Wroc?aw, Polandb Institute of Chemistry, University of Opole, Oleska 48, 45-951 Opole, Polandc Institute of Experimental Physics, University of Wroc?aw, 9 Max Born Square, 50-204 Wroc?aw, Polandd Institute of Low Temperature and Structure Research of the Polish Academy of Science, Okólna 2, 50-950 Wroc?aw, Poland |
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| Abstract: | A sequence of structural phase transitions in (CH3)2NH2]3Bi2Cl9] (DMACB) is established on the basis of differential scanning calorimetry (DSC) and dilatometric studies. Four phase transitions are found: at 367/369, 340/341, 323/325 and 285/292 K (on cooling/heating). The crystal structure of DMACB is determined at 350 K. It crystallizes in monoclinic space group P21/n: a=8.062(2), b=21.810(4), c=14.072(3) Å, β=92.63(3)°, Z=4, R1=0.0575, wR2=0.1486. The crystal is built of the double chain anions (“pleated ribbon structure”) and the dimethylammonium cations. Dielectric studies in the frequency range 75 kHz-900 MHz indicate relatively fast reorientation of the dimethylammonium cations over the I, II, III and IV phases. Infrared spectra are recorded in the temperature range 40-300 K and analyzed in region assigned to the symmetric and asymmetric NC2 stretching vibrations. Optical observations show the existence of the ferroelastic domain structure over all phases below 367 K. The possible mechanisms of phase transitions are discussed on the basis of presented results. |
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| Keywords: | Halogenobismuthate(III) Structure Phase transition Ferroelastic |
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