Dielectric Dispersion Studies in (CH3)2NH2Ga(SO4)2- 6H2O(DMAGaS) Crystal

Czapla, Z.; Tchukvinskyi, R.

doi:10.12693/aphyspola.93.527

Cited by 9 publications

(10 citation statements)

References 6 publications

(14 reference statements)

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“…Near T c1 and in the ferroelectric phase, the ferroelectric dispersion overlaps with the domain wall dispersion and causes a complex dielectric spectrum [2]. Very similar results have been obtained by Czapla and Tchukvinskyi [9]. Dielectric investigations of ferroelectric (CH 3 ) 2 NH 2 Al(SO 4 ) 2 Á 6H 2 O crystals have shown a critical slowing-down process of polarisation, with an extremely long relaxation time for the dipole system ( ¼ 1.6 Â 10 À7 s at the phase transition temperature).…”

Section: Introductionsupporting

confidence: 81%

Dielectric properties of a DMAGaS/DMAAS mixed crystal

et al. 2005

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Dimethylammonium gallium sulphate hexahydrate (DMAGaS) and dimethylammonium aluminum sulphate hexahydrate (DMAAS) are isomorphous and ferroelastic at room temperature. They both show an orderdisorder type transition into a ferroelectric phase, but only DMAGaS exhibits a further first-order transition into a low-temperature nonferroelectric phase. In this article, the results of dielectric measurements of the mixed crystal (DMAGaS) 0.9 (DMAAS) 0.1 are presented. It has been found that the phase transition temperatures are T c1 ¼ 138 K and T c2 ¼ 104 K. Debye type dielectric dispersion has been observed above the first phase transition. In the intermediate ferroelectric phase, dielectric dispersion has been described using the Cole-Cole formula. In the intermediate phase, two relaxational processes have been observed. At the first phase transition, the soft mode softens up to 411 kHz. The activation energy of the soft mode in the paraelectric phase has been obtained: ÁF/k ¼ 1248 K (ÁF ¼ 0.108 eV), which is very close to pure DMAGaS. At low temperatures below T c2 a low-frequency dielectric dispersion, typical for dipolar glass, has been observed.

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Section: Introductionsupporting

confidence: 81%

Dielectric properties of a DMAGaS/DMAAS mixed crystal

et al. 2005

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“…At the same time, available experimental data allow to calculate some parameters of the phenomenological theory: T 0 c ¼ 34:5 K, T * ¼ 144:5 K, a 0 ¼ 0:25 Â 10 À3 K À1 , x ¼ 12:79. 8), beside the jumps at T c1 ¼ 136 K and T c2 ¼ 119 K one can observe an anomaly of dðDnÞ 1 characteristic of a phase transition at T 1 ¼ 96:5 K. A comparison of the obtained transition temperatures with the data of dielectric investigations performed at cooling (T c1 ¼ 133 K and T c2 ¼ 113 K [9]) testifies the presence of a considerable temperature hysteresis for both phase transitions limiting the ferroelectric phase. Indeed, in the temperature dependence of the optical birefringence mea- Al (a, b), Ga (c)) crystals sured at heating in the direction, parallel to the ferroelectric axis (Fig.…”

Section: Dielectric and Birefringent Properties Phenomenological Desmentioning

confidence: 65%

Dielectric and Electrooptic Properties of the DMAMeS (Me = Al, Ga) Crystals in the Region of Low Temperature Phases

Kapustianik

Sveleba

Stasyuk

et al. 2001

phys. stat. sol. (b)

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This paper presents the results of investigations of the dielectric, birefringent and electrooptic properties of NH 2 (CH 3 ) 2 Me(SO 4 ) 2 Á 6H 2 O (Me ¼ Al, Ga) crystals. The data obtained are compared with the predictions of a phenomenological theory. In particular, the temperature behaviour of the dielectric susceptibility components and their anomalies in the vicinity of phase transition points were investigated in details. The specific behaviour of the studied parameters in the low temperature region was related to the coexistence of ferroelectric and antiferroelectric ordering of the dimethylammonium groups carrying a dipole moment. phys. stat. sol. (b) 228, No. 3, 785-798 (2001) # WILEY-

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“…Successive phases are denoted as I, II, and III. At both phase transitions, 136 and 116 K, discontinuous changes of dielectric permittivity, spontaneous polarization, ultrasound velocity and linear dimensions of DMAGaS samples were observed [3][4][5][6][7][8][9][10]. The symmetry of phases I, II are 2/m and m, respectively [1,2,[11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

Dilatometric and Optical Properties of (CH3)2NH2Ga(SO4)2 � 6H2O Crystals in Paraelectric and Ferroelectric Phases

Podsiadła

Czapla

Andriyevsky

et al. 2001

phys. stat. sol. (b)

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Investigations of the temperature dependences of the dimension L i , optical path difference D ij ¼ L i (n j À 1), and refractive indices n j have been carried out for DMAGaS crystal, (CH 3 ) 2 NH 2 Ga(SO 4 ) 2 Á 6H 2 O, in the range of 115-293 K for three principal directions of the optical indicatrix (i, j ¼ p, m, g). The minima of the temperature dependences of anisotropy degree indices of the linear thermal expansion A a and refractive indices A nÀ1 at temperature T c reflect a small disordering of the crystal in the phase transition region. The coefficients of spontaneous linear electrostriction Q L have been found to be almost constant in the temperature range below T c % 136 K. The molecular refraction R, as a parameter of electron polarization due to high frequency light excitation, remains unchanged in the frame of 0.2% in the temperature range of 115-293 K.

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Dielectric Dispersion Studies in (CH₃)₂NH₂Ga(SO₄)₂- 6H₂O(DMAGaS) Crystal

Cited by 9 publications

References 6 publications

Dielectric properties of a DMAGaS/DMAAS mixed crystal

Dielectric properties of a DMAGaS/DMAAS mixed crystal

Dielectric and Electrooptic Properties of the DMAMeS (Me = Al, Ga) Crystals in the Region of Low Temperature Phases

Dilatometric and Optical Properties of (CH3)2NH2Ga(SO4)2 � 6H2O Crystals in Paraelectric and Ferroelectric Phases

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