The dielectric dispersion in glycine phosphite crystal over the frequency range 30-1000 MHz is presented. Ferroelectric dispersion of the Debye type along the b-axis occurs in the microwave-frequency region and is caused by a single relaxational soft mode. The powder IR (at low temperatures between 300 and 14 K) and FT Raman spectra in the region between 4000 and 80 cm −1 are measured. DSC measurements for the GPI and deuterated crystals are performed. The results confirm the order-disorder nature of a proper ferroelectric phase transition of second order.

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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.

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The crystals of (CH,NH,),Bi,Br, have been grown which at room temperature are isomorphous with Cs,Bi,Br, and (CH,NH,),Sb,Br,.The space group is P3m1, a = 0.807, c = 1.008 nm, V = 0.5685 nm3, Z = 1 . The crystals reveal, when cooling, three phase transitions at 188f0.5, 140f1, and 101.5 f 0.5 K. The high temperature phase (I) behaves as a plastic one with respect to a freedom of rotation of methylammonium cations. The two high temperature transitions I+ I1 and II+ 111 can be related, similarly to (CH,NH,),Sb,Br,, to a freezing of reorientation of those cations. At 101.5 K a transition to the improper ferroelectric phase IV was discovered. The features of this phase are non-typical and the nature of the transition is unknown.

Halogenoantimonates(iii) and halogenobismuthates(iii) are a highly versatile class of organic–inorganic hybrid materials, applicable in optoelectronics and switchable dielectric devices.