Ferroelectric properties of (C5H5NH)5Bi2Br11

Abstract

Articles you may be interested in 4,4′-, 5,5′-, and 6,6′-dimethyl-2,2′-bipyridyls: The structures, phase transitions, vibrations, and methyl group tunneling of their complexes with chloranilic acid J. Chem. Phys. 135, 044509 (2011); 10.1063/1.3613640Dielectric and structural characterization of high-temperature ferroelectric xBi(Zn1/2Ti1/2)O3−yPbZrO3-zPbTiO3 perovskite ternary solid solution A new pyridinium compound, (C 5 H 5 NH͒ 5 Bi 2 Br 11 , has been synthesized. The x-ray diffraction studies indicate that its structure is built up of four independent pyridinium cations and isolated Bi 2 Br 11 5Ϫ groups. At room temperature it crystallizes in the monoclinic space group P2 1 /n. Two phase transitions of second-and first-order type are detected by the differential scanning calorimetry measurements at 118 and 405/403 K ͑on heating-cooling͒, respectively. The corresponding anomalies in the linear thermal expansion at 118 and 405 K are observed along three crystallographic directions. The dielectric investigations reveal dielectric absorption and dispersion in the radio-frequency region. The experimental results were analyzed on the basis of dielectric formula which represents the sum of two independent relaxators. The pyroelectric measurements reveal that (C 5 H 5 NH͒ 5 Bi 2 Br 11 becomes ferroelectric below 118 K and is characterized by the appearance of spontaneous polarization of the order of 3•10 Ϫ3 C/m 2 along the b axis.

NMR Study of Phase Transitions in New Ferroelectric Crystal—(C5H5NH)5Bi2Br11

“…Lately, we have discovered a new pyridinium analogs with the same stoichiometry, namely (C 5 H 5 NH) 5 Bi 2 Br 11 (abbreviation, PBB) [5]. At room temperature (293 K) it crystallizes in the monoclinic symmetry, space group P2 1 /n Z = 2.…”

Tris(allylammonium) Hexabromobismuthate(III) – Crystal Structure, Phase Transitions and Thermal, Dielectric, Vibrational and 1H NMR Properties Over a Range of Temperatures

“…[10][11][12][13][14][15] Generally, the ferroelectricity of these subgroups of crystals is due to the dynamics of the organic cations, thus the paraelectricferroelectric phase transitions are characterised by an "order-disorder" mechanism. The ferroelectricity appears in the compounds comprised of different types of cations, such as small size alkylammonium (methyl-, dimethyl-and trimethylammonium) and unsubstituted heteroaromatic moieties (imidazolium and pyridinium).…”

Phase Transitions Mechanism and Distortion of SbCl6 3– Octahedra in Bis(n-butylammonium) Pentachloroantimonate(III) (C4H9NH3)2[SbCl5]

“…Typically the mechanisms of phase transitions are complex, because the dynamics of both sublattices may be involved. The compounds are molecular-ionic salts, with anionic sublattices composed of deformed MX 6 3− octahedra or MX 5 2− square pyramids, which may be isolated or connected with each other by corners, edges or faces, forming various structural geometries [3,7].…”

“…The lone electron pair may be easily deformed from the initial symmetry as a result of a formation of M-X-M (M = Bi, or Sb; X = Cl, Br or I) bonds. When two octahedra are joined together having common (X) halogen atoms the bridging M-X bond length is increased, whereas the oppo- 3 Cl 9 ], where in the octahedral configuration of the antimony atom there are three bridging Sb-Cl bonds, the length of which is 2.915(10)Å, whereas the three terminal ones, have a length of 2.446(1)Å [11]. It should be noted that the increase of bond lengths compared to not deformed octahedron in this case is 0.27Å, whereas the decrease in length of the opposite bonds is 0.20Å.…”