Search results

1

Domain Structure and Birefringence in Pyridinium Perchlorate and Pyridinium Fluoroborate Single Crystal

100%

Kosturek B., Czapla Z.

Acta Physica Polonica A

|

2004

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vol. 106

|

issue 4

529-534

EN

Pyridinium perchlorate and pyridinium fluoroborate were grown and their successive phase transitions were studied by means of polarized microscopic observations and measurements of linear birefringence temperature changes. The microscopic observations revealed domain structure appearance at 245 K and 238.7 K for pyridinium perchlorate and pyridinium fluoroborate, respectively. This domain structure exists also in lower phases. Birefringence measurements confirmed two first-order phase transitions at 245.3 K and 231.5 K for pyridinium perchlorate and two continuous phase transitions at 238.7 K and 205.4 K for pyridinium fluoroborate.

2

Dielectric Properties of NaNH_{4}SO_{4}·2H_{2}O-NaNH_{4}SeO_{4}·2H_{2}O Mixed Crystals Mixed Crystals

100%

Czupiński O., Mróz J.

Acta Physica Polonica A

|

1993

|

vol. 84

|

issue 6

1125-1130

EN

The mixed crystals of NaNH_{4}SO_{4}·2H_{2}O-NaNH_{4}SeO_{4}·2H_{2}O were grown and their properties were investigated. Dielectric and differential thermal analysis studies allowed us to construct the phase diagram of the system with molar fraction, x, of NaNH_{4}SeO_{4}·2H_{2}O as a parameter. Nonlinear dependence of T_{c} versus composition was found.

3

Influence of Defects on Ferroelastic Phase Transition in InI Single Crystals

100%

Kolinko M., Kityk I., Kozhljuk A.

Acta Physica Polonica A

|

1993

|

vol. 84

|

issue 6

1065-1069

EN

The influence of the defect subsystem on the behaviour of the structural incommensurate phase in InI single crystals was investigated. The correlation between the incommensurate parameter ζ and the piezooptical π_{2222} tensor component was revealed.

4

Dielectric Dispersion in Ferroelectric Glycine Phosphite

100%

Tchukvinskyi R., Czapla Z., Sobiestianskas R., Brilingas A., Grigas J., Baran J.

Acta Physica Polonica A

|

1997

|

vol. 92

|

issue 6

1191-1196

EN

Dielectric dispersion in ferroelectric hydrogen bonded glicyne phosphite crystal was investigated in the frequency range 100 Hz - 27 GHz. Dielectric relaxation of Debye type observed in the paraelectric phase shows a critical slowing down of the polarization fluctuations. The relaxation frequency decreases with temperature according to f_{s} = 0.305(T-T_{0}) GHz in the paraelectric phase. The activation energy for flipping dipole motion ΔU = 2.07kT_{c} confirms order-disorder character of the phase transition. In the ferroelectric phase pronounced low frequency (100 Hz - 1 MHz) dispersion related to domain contribution to permittivity was found.

5

Simultaneous Pyroelectric and Dilatometric Studies of Phase Transitions in Triglycine Sulphate and Glycine Posphite Crystals

100%

Andriyevsky B., Kardash V., Dacko S., Czapla Z.

Acta Physica Polonica A

|

2001

|

vol. 99

|

issue 5

593-600

EN

Temperature dependences of the linear dimension L(T) and spontaneous polarization P_s(T) for triglycine sulphate and glycine posphite single crystals have been measured in the same run of temperature. A decrease in the spontaneous electrostriction coefficient Q_L of both crystals studied is displayed when approaching the corresponding phase transition point T_c. A temperature dependence of the coefficients Q_L(T) shows that the rates of temperature changes of displacement of the atomic complexes of corresponding crystal structure forming the square of spontaneous polarization P_s^2 (primary order parameter) and the displacements of all atomic complexes forming the spontaneous linear thermal expansionδ L_s/L (secondary order parameter) are different. The applying external electric field E=3×10 ^5 V/m to triglycine sulphate crystal does not influence essentially the temperature dependence of Q_L(T) in the temperature range of phase transition below T_c.

6

Characterization of Ferroelectric Phase Transition in Deuterated Glycine Phosphite Crystal

100%

Furtak J., Dacko S., Czapla Z.

Acta Physica Polonica A

|

2003

|

vol. 104

|

issue 1

67-72

EN

Dielectric, dilatometric, and ultrasonic studies around the ferroelectric phase transition at 319 K were done. Measurement of relative electric permittivity showed the existence of a strong bias field which causes in studied samples some diffused character of phase transition. However, all presented measurement confirmed the continuous character of phase transition. The obtained data are similar to those received earlier in the case of hydrogenated glycine phosphite crystal.

7

Chaos near Structural Phase Transition

100%

Beige H., Diestelhorst M., Forster R., Albers J., Petersson J.

Acta Physica Polonica A

|

1992

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vol. 81

|

issue 3

413-418

EN

The studies of nonlinear dynamical dielectric properties of TGS which exhibits chaotic behaviour have been presented. The recorded phase portraits obtained from experiment are compared with the calculations based on different assumptions using a computer.

8

Influence of Mechanical Stress on the Birefringence Properties of (N(CH_{3})_{4})_{2}ZnCl_{4} Crystals

100%

Polovinko I., Sveleba S., Vlokh O., Zhmurko V.

Acta Physica Polonica A

|

1992

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vol. 81

|

issue 3

409-412

EN

The influence of applied mechanical stress on the birefringence of (N(CH_{3})_{4})_{2}ZnCl_{4} crystal in the temperature region of its incommensurate phase was investigated using Senarmonth's method (λ = 633 nm). The value of pinning force for the samples with different defectiveness was experimentally determined.

9

Dielectric Dispersion Studies in (CH_{3})_{2}NH_{2}Ga(SO_{4})_{2} - 6H_{2}O(DMAGaS) Crystal

100%

Czapla Z., Tchukvinskyi R.

|

EN

The paper presents the new data of dielectric dispersion in DMAGaS crystal. The very pronounced dispersion above T_{c1} =136 K is observed in the frequency range 100 Hz-30 MHz with a single relaxation process. The relaxation time τ of an electric dipole reaches 2.17×10^{-7} s at the T_{c1}. The activation free energy ΔF of the dipoles is estimated to be equal to 0.087 eV. The order-disorder type of phase transition is confirmed.

10

On the Phase Transitions in Cs_2CdBr_4: Dielectric, Dilatometric and Optical Studies

100%

Dacko S., Czapla Z.

Acta Physica Polonica A

|

2003

|

vol. 103

|

issue 4

387-392

EN

Dielectric, dilatometric measurement and polarized microscopic observation were performed for single crystal of Cs_2CdBr_4. These investigations showed clearly the phase transitions at 252 K, 236 K and 153 K. The jump-like change of the crystal volume corresponding to the first-order phase transition was found at temperature of 236 K. Ferroelastic domain structure was observed along the a-axis below 236 K and it is preserved below the transition at 153 K. Observation along the c-axis revealed new domain structure below 153 K.

11

Dielectric Investigation of Glycine Phosphite Crystal

100%

Czukwinski R., Czapla Z., Styrkowiec R.

|

EN

The complementary measurements of the dielectric dispersion in ferroelectric phase of glycine phosphite crystal at the frequency range of 200 Hz - 1 MHz have been carried out. The analysis of the dielectric spectra of the low frequency relaxation process showed that it can be fitted by two Debye-type relaxators. The activation energy of the both processes has been calculated. The observed behaviour of the relaxators suggests that they are connected with a domain structure; one with the growth of the nuclei whereas the second with the domain wall movement.

12

Pyroelectric and Dilatometric Studies on the Low Temperature Ferroelectric Phase Transition of (CH_3NH_3)_5Bi_2Br_{11}

100%

Dziedzic J., Mróz J., Jakubas R.

Acta Physica Polonica A

|

2005

|

vol. 108

|

issue 3

505-511

EN

The results of the linear thermal expansion studies on (CH_3NH_3)_5Bi_2Br_{11} single crystals in the temperature range 60-340 K are presented. The thermal anomaly in the vicinity of 77 K is assigned to the phase transition classified as close to first order type. The pyroelectric measurements of (CH_3NH_3)_5Bi_2Br_{11} were carried out in the range of 45-320 K along the a- and c-axis. The step-like change in the spontaneous polarization along the a-axis at 77 K indicates a discontinuous character of ferroelectric transition.

13

Temperature Dependence of the Optical Activity of Pure and Deuterated Rochelle Salt Crystals

63%

Koralewski M., Szafrański M.

Acta Physica Polonica A

|

2002

|

vol. 102

|

issue 3

409-417

EN

Temperature dependence of the optical rotatory power (ρ) along the optical axis of pure and deuterated Rochelle salt single crystals has been given. Three phases of both crystals were examined and found to be optically active. The relation between spontaneous electrogyration (ρ_s) and spontaneous polarization (P_s) can be described by {ρ_s}∝P_s^2. Moreover, the antipolar domains of pure and deuterated ferroelectric Rochelle salt crystals were found of the rotation twin-type not occurring in the enantiomorphic form, in contrast to those in other ferroelectric crystals, e.g., TGS-type and Pb_5Ge_3O_{11}.

14

Model of Temperature Dependence of Spontaneous Polarization of Thiourea Monocrystal in Phase I

63%

Śliwa I., Wanarski W.

Acta Physica Polonica A

|

2012

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vol. 122

|

issue 1

184-189

EN

In this paper we present a model of spontaneous polarization appearing in the crystal of thiourea in phase I, constructed on the basis of the molecular field theory, with the use of the Boltzmann statistics. The model employs the potential energy of interaction between two nonpunctual molecular electric dipoles performing reorientations within the constraints specified by the experimentally determined structural data. The temperature dependences of the spontaneous polarization for different values of the hydrostatic pressure and for different γ-ray doses were obtained. A comparison between theoretical and experimental results permitted calculation of the parameters of the theory presented.

15

The Effect of Ageing Process on the Electrogyration of Deuterated Triglycine Sulphate Crystals

63%

Koralewski M., Stankowska J., Habryło S.

Acta Physica Polonica A

|

2002

|

vol. 101

|

issue 2

243-248

EN

The paper reports results of a study of optical activity and ferroelectric properties of rejuvenated and aged deuterated triglycine sulphate crystals. A possibility of monitoring of the ferroelectric crystal ageing process by optical measurements was proved. A linear relation between optical rotatory powerρ and spontaneous polarization P_s was confirmed for aged and rejuvenated deuterated triglycine sulphate crystals.

16

On the Relation of the Order-Parameter and Transition Temperature in Ferroelectric Solid Solutions

63%

Windsch W., Braeter H.

Acta Physica Polonica A

|

1994

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vol. 86

|

issue 3

393-406

EN

Within the framework of the model of coupled anharmonic oscillators a ferroelectric solid solution is described with only a few parameters. In high-temperature approximation a linear relation between the square of the order parameter and the transition temperature is obtained. This is illustrated by an application to several modified lead titanate ceramics, the linear relation between transition temperature and tetragonal lattice deformation is verified. For tris-sarcosine calcium chloride (bromide) (TSCC/B) at very low temperatures the expected deviation from the classical behaviour is seen.

17

Pyroelectricity in Non-Central Crystals

63%

Pereverzeva L., Poplavko Y., Prokopenko Y., Chepiliko A.

Acta Physica Polonica A

|

1993

|

vol. 84

|

issue 2

287-291

EN

Unit cell electric arrangement of piezoelectric crystals may be described by various multipole/octupole/dipole electric moments which corresponds to a three/two/one-dimensional intrinsic polarity respectively. Such a latent polar structure is totally self-compensated in piezoelectrics if they are mechanically free, but it is non-compensated in pyroelectrics and ferroelectrics. Uniform but anisotropic partial clamping destroys a total self-compensation of non-central crystal intrinsic polarity. This decompensation allows to observe a polar response that is a "dipole projection" ΔP_{i} from, broken by clamping, spatial polar arrangement of piezoelectrics.

18

On Linear Birefringence Anomalies in Crystals of Triglycine Family

63%

Przesławski J.

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vol. 95

|

issue 6

997-1004

EN

Temperature dependence of the linear birefringence in TGS crystal family has been studied with a high temperature resolution. Temperature derivatives of the linear birefringence are compared with the specific heat transients measured for triglycine sulphate, triglycine selenate, and triglycine fluoberyllate crystals. Detailed studies revealed an anomaly of the linear birefringence at about 310 K for two cuts (a*- and c-cut) of the TGS crystal.

19

Anomalous Non-linear Dielectric Behaviour of LATGS Crystals

63%

Cach R., Mróz J., Haden D.

Acta Physica Polonica A

|

1991

|

vol. 79

|

issue 6

905-914

EN

The dielectric permittivity in a biasing electric field and also the spontaneous polarization of LATGS crystals are measured near the ferroelectric phase transition. It is demonstrated that L-alanine admixtures change the parameters of dielectric state equation. It is shown that the bias field value decreases while approaching the phase transition temperature from the para-electric phase. The effective non-linearity coefficient B, near Tc, depends on electric field direction. This anomalous non-linear behaviour can be explained assuming asymmetric bias field dependence on external electric field.

20

Effect of Uniaxial Pressure on the Ferroelectric Phase Transition in Pb_5Ge_3O_{11}:Ba Crystals

63%

Molak A., Koralewski M., Saunders G., Juszczyk W.

Acta Physica Polonica A

|

2005

|

vol. 108

|

issue 3

513-520

EN

The effect of uniaxial pressure up to 1 kbar applied perpendicular and parallel to c-axis, on the Curie temperature and electric permittivityε_c of Ba-doped Pb_5Ge_3O_{11} single crystals was investigated. The Curie temperature decreases with uniaxial pressure and the coefficientγ_i (γ_i ≡ δ T_{c}/δ X_i) is determined as -7 and -11 K kbar^{-1} for the b- and c-axes, respectively. It was found that uniaxial pressure increases the phase transition diffuseness and the tricritical point cannot be achieved for this pyroelectric and ferroelectric single crystal.

Refine search results

Domain Structure and Birefringence in Pyridinium Perchlorate and Pyridinium Fluoroborate Single Crystal

Dielectric Properties of NaNH_{4}SO_{4}·2H_{2}O-NaNH_{4}SeO_{4}·2H_{2}O Mixed Crystals Mixed Crystals

Influence of Defects on Ferroelastic Phase Transition in InI Single Crystals

Dielectric Dispersion in Ferroelectric Glycine Phosphite

Simultaneous Pyroelectric and Dilatometric Studies of Phase Transitions in Triglycine Sulphate and Glycine Posphite Crystals

Characterization of Ferroelectric Phase Transition in Deuterated Glycine Phosphite Crystal

Chaos near Structural Phase Transition

Influence of Mechanical Stress on the Birefringence Properties of (N(CH_{3})_{4})_{2}ZnCl_{4} Crystals

Dielectric Dispersion Studies in (CH_{3})_{2}NH_{2}Ga(SO_{4})_{2} - 6H_{2}O(DMAGaS) Crystal

On the Phase Transitions in Cs_2CdBr_4: Dielectric, Dilatometric and Optical Studies

Dielectric Investigation of Glycine Phosphite Crystal

Pyroelectric and Dilatometric Studies on the Low Temperature Ferroelectric Phase Transition of (CH_3NH_3)_5Bi_2Br_{11}

Temperature Dependence of the Optical Activity of Pure and Deuterated Rochelle Salt Crystals

Model of Temperature Dependence of Spontaneous Polarization of Thiourea Monocrystal in Phase I

The Effect of Ageing Process on the Electrogyration of Deuterated Triglycine Sulphate Crystals

On the Relation of the Order-Parameter and Transition Temperature in Ferroelectric Solid Solutions

Pyroelectricity in Non-Central Crystals

On Linear Birefringence Anomalies in Crystals of Triglycine Family

Anomalous Non-linear Dielectric Behaviour of LATGS Crystals

Effect of Uniaxial Pressure on the Ferroelectric Phase Transition in Pb_5Ge_3O_{11}:Ba Crystals