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Szafrański, Marek

doi:10.1103/physrevb.72.054122

Cited by 43 publications

(11 citation statements)

References 21 publications

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“…fig. 2) very broad huge anomaly which suggested presence of a few overlapping peaks which is consistent with DTA plots [1] . Next we decrease heating rate to 0.1 K/min and as a result obtain -during heating cycle-two sharp maxima -at 356.2 K and 362 K. In the cooling run the DSC behaviour of the crystal shows single peak (see Fig.…”

Section: Dsc Measurementsupporting

confidence: 82%

“…Following the results presented by Szafranski [1] one can see that there exists several temperature ranges with the lattice unstable structure which give the possibility to form additional non-centrosymmetry. Comparing the obtained DSC and PISHG data one can conclude a high sensitivity of these methods to the observed phase transformations caused by the displacements of the guanidine cations from their high-symmetry sites in the tetragonal phase together with local re-ordering of the sulphate and chlorum groups [1]. Because there exists a relatively large amount of the disordered phase manifestation of the PISHG would be more prominent.…”

Section: Resultssupporting

confidence: 57%

“…As DSC/MDSC methods are convenient in practice they are widely used: polymer transformations, crystallization -melting features, resins curing, protein denaturation, glass transitions are among fields of this methods application [1][2][3][4]. At the same time the optical methods are able to indicate also transformations connected with interactions of phonon modes with excited states.…”

Section: Introductionmentioning

confidence: 99%

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Optical and thermal tools for the phase transitions detection in the guanidine compounds

Brągiel

Piasecki

Kityk

2007

J. Phys.: Conf. Ser.

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Synthesis and characterization of £A-(2-cyano-1-methyl-3-{2-{{(5-methylimidazol-4-yl)methyl}thio}ethyl)guanidine copper(II) sulfate tetrahydrate Sentot B Rahardjo, Teguh Endah Saraswati, Edy Pramono et al. . In this report we present results of DSC measurements in heating-cooling regime with relatively low temperature rates-0.3 K/min and 0.1 K/min. We compare the measured by us the DSC results with temperature dependent photo induced second harmonic generation (PISHG) data. The investigations show that at lowest heating temperature changes velocity (0.1 K/min) we obtain two wide peaks temperature separated . We conclude from this DSC measurement that [C(NH 2 ) 3 ] 4 Cl 2 SO 4 single crystals undergo a two-step phase transitions. We have received a similar temperature splitting of the observed phase transformations and a 15 K shift between the temperature PISHG dependences and the principal DSC maxima. IntroductionDifferential scanning calorimetry (DSC) and its modulated DSC (MDSC) version are known to be sensitive tools for studies of phase transitions, especially in the cases of strong electron-phonon anharmonic interactions in vicinity of critical temperature points. As DSC/MDSC methods are convenient in practice they are widely used: polymer transformations, crystallization -melting features, resins curing, protein denaturation, glass transitions are among fields of this methods application [1][2][3][4]. At the same time the optical methods are able to indicate also transformations connected with interactions of phonon modes with excited states. Due to this reason the optical and especially nonlinear optical methods become more and more popular for detection of different phase transitions [5,6]. The higher order optical effects are more sensitive than this of lower order a two-photon absorption and a third harmonics generation [7]. However, there is a strong shortcoming for the third harmonic generation: a dozens of samples, including semiconductors and even dielectrics, are nontransparent for the tripled frequency wavelengths. The other effect depending on third rank polar tensor is also optical second harmonic generation (SHG). A limitation in this case presents randomly oriented samples or centro-symmetrical crystals. A solution, in this case may be an optical poling or a photoinduced second harmonic generation (PISHG) [8,9]. The main goal of this paper is to compare the results of DSC and PISHG measurements and to discuss a capability of both these methods to detect properly phase transition temperature and its kind for ferroelectrics. At first a brief description of DSC scans for the pyridazine perchlorate single crystals is given to prove with earlier permittivity data, that when used with extremely small heating rates is able to indicate transition temperatures very precisely. After this both DSC and PISHG methods are applied to study tetraguanidine dichloro-sulfate: [C(NH 2 ) 3 ] 4 Cl 2 SO 4 single crystals. The discrepancies between the temperature-dependent pictures obtained from the both sets are t...

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Section: Dsc Measurementsupporting

confidence: 82%

Section: Resultssupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

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Optical and thermal tools for the phase transitions detection in the guanidine compounds

Brągiel

Piasecki

Kityk

2007

J. Phys.: Conf. Ser.

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“…Only a few attempts at theoretical determination of the spontaneous polarisation have been made. Its value can be estimated in the displacement type ferroelectrics when their crystalline structure is known [1][2][3][4]. In the displacive type ferroelectrics, an asymmetric shift of anions and cations in the elementary cell induces a dipole moment, and the product of this dipole moment and the elementary cell volume gives an approximate value of spontaneous polarisation.…”

Section: Introductionmentioning

confidence: 99%

Polarisation and Energy Barriers in Ferroelectric Pyridinium Perchlorate

et al. 2008

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Polycrystalline sample of pyridinium perchlorate was studied by NMR method in the temperature range from 133 to 313 K. Assuming a reorientation of pyridinium cations over inequivalent potential energy barriers in the low-temperature and intermediate phases a temperature dependence of an asymmetry parameter was determined from analysis of 2 H line shape. By using the known potential shape and population of its minima, a temperature dependence of the spontaneous polarisation was calculated. The polarisation determined in this way compared with that measured by the pyroelectric effect revealed the mixed type of ferroelectricity in the crystal studied: the order-disorder and displacive one.

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“…Frequency dependence of polarization switching is another essential properties for potential application of ferroelectrics. For most molecular ferroelectrics in the single‐crystal form, the polarization switching could only be achieved at the frequency lower than 500 Hz, particularly for order‐disorder ferroelectrics, such as N ‐isopropylbenzylaminium trichloroacetate at 30 Hz, (H 2 dabco)Cu(H 2 O) 6 (SeO 4 ) 2 at 400 Hz, [C(NH 2 ) 3 ]Cl 2 SO 4 at 50 Hz, Ca(NO 3 ) 2 (15‐crown‐5) at 25 Hz, [(DIPA)(18‐crown‐6)]ClO 4 and [(DIPA)(18‐crown‐6)]BF 4 (DIPA=2,6‐diisopropylanilinium) at 50 Hz . We measured the frequency dependence of P s for 1 using the thin crystals.…”

Section: Figurementioning

confidence: 99%

A Molecular Ferroelectric Showing Room‐Temperature Record‐Fast Switching of Spontaneous Polarization

Sun

Tao

et al. 2018

Angewandte Chemie

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Fast switching of spontaneous polarization (Ps) is one of the most essential requirements for ferroelectrics used in the field of data storage. However, in contrast to inorganic counterparts, the low operating frequency (<500 Hz) for molecular ferroelectrics severely hinders their large‐scale applications. Herein, for the first time, we achieved the room‐temperature fastest switching of the Ps in a new molecular ferroelectric, N‐methylmorpholinium trinitrophenolate (1), which displays notable ferroelectricity (Ps=3.2 μc cm−2). Strikingly, electric polarizations of 1 have been switched under a record‐high frequency of 263 kHz, and this performance remains stable without any obvious fatigue after ca. 2×105 switching cycles. To our knowledge, 1 is the first organic ferroelectric to switch polarization at such a high operating frequency, exceeding the majority of organic ferroelectrics, which opens up new possibilities for its potential in the field of non‐volatile memory.

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Ferroelectricity in the guanidinium compound[C(NH2)3]4
Marek Szafrański
¹

Cited by 43 publications

References 21 publications

Optical and thermal tools for the phase transitions detection in the guanidine compounds

Optical and thermal tools for the phase transitions detection in the guanidine compounds

Polarisation and Energy Barriers in Ferroelectric Pyridinium Perchlorate

A Molecular Ferroelectric Showing Room‐Temperature Record‐Fast Switching of Spontaneous Polarization

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Ferroelectricity in the guanidinium compound[C(NH2)3]4Marek Szafrański1

Cited by 43 publications

References 21 publications

Optical and thermal tools for the phase transitions detection in the guanidine compounds

Optical and thermal tools for the phase transitions detection in the guanidine compounds

Polarisation and Energy Barriers in Ferroelectric Pyridinium Perchlorate

A Molecular Ferroelectric Showing Room‐Temperature Record‐Fast Switching of Spontaneous Polarization

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Ferroelectricity in the guanidinium compound[C(NH2)3]4
Marek Szafrański
¹