0000000000924301
AUTHOR
J. Jóźków
Crystal structure, dielectric properties and molecular motions in ( i -C 4 H 9 NH 3 ) 3 Bi 2 Br 9
Abstract The crystal structure of ( i -C 4 H 9 NH 3 ) 3 Bi 2 Br 9 at room temperature has been determined and refined to R =0.036. The crystal is orthorhombic, space group Ama 2. The structure is built up of the i -butylammonium cations and isolated Bi 2 Br 9 3− anions. The complex dielectric permittivity along the a -axis has been measured between 500 Hz and 1000 MHz in the vicinity of two phase transitions at 252 and 263 K. The dielectric response close to 252 K is well described by the Debye equation. The activation energy of the reorientation of the i -butylammonium cations is found to be 0.68 eV. The temperature dependencies of the proton relaxation time T 1 and of the second moment of…
Phase transitions in i-butylammonium halogenoantimonate(III) and bismuthate(III) crystals
Abstract Differential scanning calorimetry, dielectric, thermal expansion, infrared and preliminary X-ray diffraction studies on i-butylammonium halogenoantimonate(III) and bismuthate(III) crystals are reported. All crystals: (i-C4H9NH3)2BiCl5, (i-C4H9NH3)2SbBr5, (i-C4H9NH3)3BiCl6, (i-C4H9NH3)3Bi2Br9, (i-C4H9NH3)3Sb2Br9, show one or more structural phase transitions of first order type. The values of the transition entropies suggest that the most of the phase transitions are of the order-disorder type. The infrared studies confirmed the contribution of the i-butylammonium cations in the phase transition mechanism.