Critical behaviour in (BPI)<sub>x</sub>(BP)<sub>1−x</sub>

Santos, Mónica; Azevedo, J.C.; Almeida, A.; Chaves, M. R.; Pires, A. R.; Müser, H. E.; Klöpperpieper, A.

doi:10.1080/00150199008018785

Cited by 52 publications

(26 citation statements)

References 8 publications

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“…Dielectric measurements [41,[43][44][45][46] revealed proton glass behaviour for x = 0.85, 0.80, 0.60, 0.50, and 0.40. Very recently, a systematic study of the dielectric properties of compounds of the series (BP) 1-x (BPI) x was presented [45] in the paraelectric phase, and compared with the predictions of three microscopic models: the quasi-one-dimensional Ising model without disorder [47][48][49], the SherringtonKirkpatrick model [50] and the quasi-one-dimensional random-bond random-field Ising model [51].…”

Section: Dielectric Dispersion In Relaxorsmentioning

confidence: 97%

Distribution of relaxation times of relaxors: comparison with dipolar glasses

Banys

Grigalaitis

Mikonis

et al. 2009

Phys. Status Solidi (c)

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In the present publication we report the results of dielectric spectroscopy investigations of two classes of materials – relaxor and dipolar glasses. As model relaxor was chosen (Pb1–xLax)(ZryTi1–y)O3 (PLZT 100(x/y/1–y)). The real distribution function of the relaxation times f (τ) of the relaxor ferroelectric ceramics PLZT 8/65/35 and 9.5/65/35 was calculated from the dielectric measurements results in the wide frequency range (101–1012 Hz). Below the Burns temperature TB ≅ 620 K, when the clusters begin to appear on cooling, the distribution function of the relaxation times is symmetrically shaped. On cooling the dispersion and loss spectra strongly broaden and slow down, the f (τ) function becomes asymmetrically shaped and the second maximum appears. The width of the f (τ) function was calculated at different temperatures. The longest relaxation times diverge according to the Vogel‐Fulcher law with the freezing temperature 299 K and 252 K for the 8/65/35 and 9.5/65/35 samples, respectively. The shortest relaxation time is about 10–12 s and it remains almost temperature independent. Similar behaviour was observed in dipolar glasses betaine phosphate betaine phosphite (BP/BPI). Much more information was obtained from two dimensional distribution of the relaxation times. This confirmed Meyer–Neldel law in relaxors and dipolar glasses. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Section: Dielectric Dispersion In Relaxorsmentioning

confidence: 97%

Distribution of relaxation times of relaxors: comparison with dipolar glasses

Banys

Grigalaitis

Mikonis

et al. 2009

Phys. Status Solidi (c)

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“…Glassy phases, attributed to frustrated ferroelectric and antiferroelectric interactions and proton glass behaviour were proposed for some mixed crystals of BA (Betaine arsenate) and BP (Betaine phosphate) [1][2][3] and BP and BPI (Betaine phosphite) [4][5][6]. Deuterated BP-BPI compounds and γ-irradiated BP-BPI compounds have also been reported to exhibit glassy phase at low temperatures.…”

Section: Introductionmentioning

confidence: 95%

“…It undergoes the first phase transition at 365 K from a paraelectric high temperature phase having a P2 1 /m symmetry (Z = 2) into an antiferrodistortive phase with P2 1 /c symmetry and a simultaneous doubling of the unit cell along the c-axis (Z = 4). The PO 4 and betaine molecules order in the antiferrodistortive phase, but the acid hydrogen atoms linking PO 4 groups remain disordered. It exhibits a second transition into ferroelectric phase with P2 1 symmetry and Z = 4 at 86 K [16][17][18] induced by the ordering of the acid hydrogen atoms in one of the double potential wells (O-H … O bonds).…”

Section: Introductionmentioning

confidence: 97%

¹H NMR spin–lattice relaxation studies in Betaine phosphate (BP) – Transition from classical to quantum rotation

Ramanuja¹,

Ramesh²,

Ramakrishna³

2006

Physica Status Solidi (b)

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We report here the results of our 1 H NMR spin-lattice relaxation time (T 1 ) studies in betaine phosphate which is ferroelectric below 86 K and antiferroelectric below 81 K. The experiments have been carried out in the temperature range 300 to 4 K, at two Larmor frequencies 11.4 and 23.3 MHz. The T 1 data (300 -100 K) has been analysed using modified BPP equation based on Ikeda's model. CH 3 protons are found to relax other protons via spin diffusion. The low temperature (T < 100 K) T 1 data has been analysed following Lourens model which considers the gradual transition from classical motions to quantum regime. At low temperatures, when classical processes tend to freeze, reorienting groups apparently have minute differences and hence create a distribution in the energy values (E a and E 01 ) and pre-exponential factors.

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“…Complex dielectric constant, pyroelectric and X-ray techniques have been used to draw the phase diagram of BPI (1Àx) BP x in the range of x from 0 to 1 [18][19][20][21][22]. Dielectric constant measurements for various values of x, as a function of temperature down to 4.2 K, show a gradual changeover from ferroelectric (FE) to orientational glass (OG) and finally to antiferroelectric (AFE) phase.…”

Section: Introductionmentioning

confidence: 99%

NMR relaxation study of disorder in condensed matter: solid solutions of betaine phosphate and phosphite

2006

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Proton NMR relaxation measurements have been carried out in anti-ferroelectric Betaine phosphate (BP), ferroelectric Betaine phosphite (BPI) and the mixed system BPI (1Àx) BP x , at 11.4 MHz and 23.3 MHz from 300 K to 80 K for x ¼ 0.0, 0.25, 0.45, 0.85, and 1.0. The temperature dependence of spin lattice relaxation time T 1 exhibits two minima as expected from the BPP model in BP and BPI. The Larmor frequency dependence of T 1 in the mixed system is rather unusual and exhibits different slopes for the low temperature wings at the two frequencies, which is a clear experimental evidence of the presence of different methyl groups with different activation energies (E a ) indicating disorder.

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Critical behaviour in (BPI)_x(BP)_1−x

Cited by 52 publications

References 8 publications

Distribution of relaxation times of relaxors: comparison with dipolar glasses

Distribution of relaxation times of relaxors: comparison with dipolar glasses

¹H NMR spin–lattice relaxation studies in Betaine phosphate (BP) – Transition from classical to quantum rotation

NMR relaxation study of disorder in condensed matter: solid solutions of betaine phosphate and phosphite

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Critical behaviour in (BPI)x(BP)1−x

Cited by 52 publications

References 8 publications

Distribution of relaxation times of relaxors: comparison with dipolar glasses

Distribution of relaxation times of relaxors: comparison with dipolar glasses

1H NMR spin–lattice relaxation studies in Betaine phosphate (BP) – Transition from classical to quantum rotation

NMR relaxation study of disorder in condensed matter: solid solutions of betaine phosphate and phosphite

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Product

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Critical behaviour in (BPI)_x(BP)_1−x

¹H NMR spin–lattice relaxation studies in Betaine phosphate (BP) – Transition from classical to quantum rotation