Critical Slowing Down in Ferroelectric Pyridinium Tetrafluoroborate

Czarnecki, P.; Szafraniak, I.

doi:10.1002/(sici)1521-3951(199809)209:1<211::aid-pssb211>3.0.co;2-f

Cited by 16 publications

(6 citation statements)

References 17 publications

(23 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similar dielectric relaxation was observed in the well ordered low temperature phases of some other pyridinium salts [17][18][19]. There are a few sources of dipoles in the compound: the pyridinium cation dipole, the thiourea host molecule dipole and distorted NO 3 anion dipole.…”

Section: Dielectric Resultssupporting

confidence: 73%

Structure, phase transitions and dielectric properties of a new inclusion compound of bis-thiourea pyridinium nitrate salt

Małuszyńska¹,

Czarnecki²

2006

Zeitschrift Für Kristallographie - Crystalline Materials

View full text Add to dashboard Cite

Inclusion compounds / Phase transitions / Bis-thiourea pyridinium nitrate salt / Single crystal structure analysis / X-ray diffraction Abstract. A structure of a new inclusion compound of bis-thiourea pyridinium nitrate salt C 5 H 6 N þ NO 3 À 2[CH 4 N 2 S] was determined by single-crystal X-ray diffraction method at 293 K, 250 K and 150 K. In high temperature phase the compound crystallizes in orthorhombic system, the two low-temperature phases are monoclinic. The sequence of phases is: Pbnm ) P2 1 /c ) P2 1 . In the orthorhombic form (I) the a axis is doubled in respect to the monoclinic forms and pyridinium and nitrate ions are partially disordered. Both low-temperature monoclinic phases (II) and (III) are ordered but twinned by pseudomerohedry. In all three phases the host lattice is built of ribbons of hydrogen-bonded thiourea molecules and nitrate anions forming channels in which the guests pyridinium cations are located. Each ribbon consists of two crystallographically independent thiourea molecules and nitrate ions. Four ribbons form a channel parallel to the c axis with approximately square cross-section. In the channel there is a stack of pyridinium cations, which planes form an inclination angle with the channel axis. The angle varies from about 90 in disordered phase I to 60 in well ordered phase (III).The dielectric spectroscopy measurements were performed on the polycrystalline sample with HP-4291A impedance analyser in the frequency range 1 MHz-1 GHz. The dielectric measurements reveal that two phase transitions occur at T 1 ¼ 287 K and at T 2 ¼ 217 K. The phase transition at T 2 ¼ 287 K is of the first order with the thermal hysteresis of 10 K at cooling and heating. The phase transition at 217 K is of the second order and the dielectric anomaly suggests the ferroelectric-paraelectric phase transition. The dielectric relaxation observed below T 2 are caused by the pyridinium cation reorientation. The dielectric relaxation time changes with the temperature according to Arrhenius low and the activation energy of the relaxation process is about 14 kJ/mol.

show abstract

Section: Dielectric Resultssupporting

confidence: 73%

Structure, phase transitions and dielectric properties of a new inclusion compound of bis-thiourea pyridinium nitrate salt

Małuszyńska¹,

Czarnecki²

2006

Zeitschrift Für Kristallographie - Crystalline Materials

View full text Add to dashboard Cite

show abstract

“…The phase transition from the disordered high-temperature phase to the ferroelectric phase is of order-disorder type [2][3][4]8]. However, the NMR [3][4][5][6][7], muon [9] and dielectric spectroscopy [5,10] measurements indicate that, in the intermediate ferroelectric phase, there are still reorientations of pyridinium cations. This indicates that this phase should be considered to be disordered, like the high-temperature phase.…”

Section: Introductionmentioning

confidence: 99%

The neutron diffraction study of pyridinium periodate at 352, 300 and 100 K

Małuszyńska

Scherf

Czarnecki

et al. 2003

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

The crystal and molecular structure of pyridinium periodate [H 5 C 5 NH] + [IO 4 ] − (hereafter referred to as PyIO 4 ) was re-determined by single-crystal neutron diffraction at 350, 300 and 100 K. The structures of the high-temperature paraelectric and the ferroelectric intermediate phase confirmed the x-ray results. The low-temperature ferroelectric phase at 100 K, for which x-ray results did not agree with dielectric measurements, was uniquely determined by neutron diffraction. The sequence of space groups and continuous phase transitions is Cmcm(I)The structure of the lowtemperature phase III is consistent with all physical measurements. The continuous phase transition at T 2 = 210 K is not just accompanied by symmetry lowering but also by reversible twinning by pseudo-merohedry. The dipole moment of the ions of the low ferroelectric phase was calculated using the Gaussian 98 program. The theoretical value agrees well with the experimental spontaneous polarization measurements from the pyroelectric effect. The PyIO 4 belongs to the order-disorder class of ferroelectrics.

show abstract

“…For many years, the pyridinium salts PyHX, where X is a monovalent anion (I − , Br − , Cl − , PF − 6 , SbF − 6 , BF − 4 , ClO − 4 , ReO − 4 etc) and PyH is the pyridinium cation ([C 5 H 5 NH] + ), have been subjects of intensive study [1][2][3][4][5]. Some of the salts show ferroelectric properties.…”

Section: Introductionmentioning

confidence: 99%

Pyridinium salt investigations under high pressure: pressure-induced phase transitions in ferroelectric pyridinium perrhenate

Czarnecki

Beskrovny

Bobrowicz-Sarga

et al. 2005

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

The properties of pyridinium perrhenate have been studied by three methods: dielectric spectroscopy, neutron powder diffractometry and NMR spectrometry under high pressure. It has been shown that under high pressure the temperatures of the two phase transitions in the crystal are shifted towards lower ones. Moreover, the results have shown the occurrence of a new high pressure phase with a triple point corresponding to the pressure of 100 MPa and the temperature of 240 K.

show abstract

Critical Slowing Down in Ferroelectric Pyridinium Tetrafluoroborate

Cited by 16 publications

References 17 publications

Structure, phase transitions and dielectric properties of a new inclusion compound of bis-thiourea pyridinium nitrate salt

Structure, phase transitions and dielectric properties of a new inclusion compound of bis-thiourea pyridinium nitrate salt

The neutron diffraction study of pyridinium periodate at 352, 300 and 100 K

Pyridinium salt investigations under high pressure: pressure-induced phase transitions in ferroelectric pyridinium perrhenate

Contact Info

Product

Resources

About