Ultrasonic Anomalies in Deuterated Betaine Phosphite near the Ferroelectric Phase Transition

Samulionis, V.; Banys, J.; Völkel, G.; Klöpperpieper, A.

doi:10.1002/(sici)1521-396x(199808)168:2<535::aid-pssa535>3.0.co;2-f

Cited by 3 publications

(4 citation statements)

References 21 publications

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“…The necessary correction of the x values is indicated for x = 0.5 in figure 2, where the arrow only gives a qualitative impression. We shall mention as well that the qualitative T C (x) dependence was preliminarily confirmed by ultrasonic measurements on further crystals with different x values by the authors of [29].…”

Section: Nmr Experiments At the High Temperature Phase Transition In ...supporting

confidence: 53%

“…This drawback is now overcome by means of additional measurements on recently grown crystals with x = 0.3 and x = 0.5, allowing us to obtain a more reliable phase diagram in the above sense. Furthermore, the temperature for the phase transition could now be calibrated more exactly by means of comparison to ultrasonic measurements on DBPI [29], which allow a precise determination of T C . For each crystal the phase transition temperature T C (x) was determined from a set of 2 H NMR spectra which were measured in dependence on the temperature in the same manner as described in [5].…”

Section: Nmr Experiments At the High Temperature Phase Transition In ...mentioning

confidence: 99%

“…Phase transition temperature T C as a function of the phosphite concentration x for different representatives of the system DBP 1−x DBPI x . The temperature was calibrated on ultrasonic measurements on DBPI [29]. Experimental data (dots) are fitted by two parameter sets of our model.…”

Section: Nmr Experiments At the High Temperature Phase Transition In ...mentioning

confidence: 99%

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A microscopic model for the concentration dependence of the antiferrodistortive phase transition in mixed betaine phosphate/phosphite crystals

Braeter

Totz

Michel

1999

J. Phys.: Condens. Matter

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The concentration dependence of the high temperature antiferrodistortive (afd) phase transition temperature TC in single crystals of the mixed crystal system betaine phosphate and betaine phosphite (BP1-xBPIx) is studied. New experimental data obtained by 2H nuclear magnetic resonance (NMR) spectroscopy on deuterated single crystals of this system confirm the nonlinear behaviour of TC(x), in particular the maximum at intermediate concentrations. A microscopic model is proposed which in extension of the treatment of a small defect concentration makes use of the virtual crystal approximation (VCA) to be applicable to the mixed crystal system DBP1-xDBPIx with finite concentrations x. By this means the experimentally observed behaviour of the afd phase transition temperature as a function of x is elucidated and the nonlinear behaviour of TC(x) is explained in agreement with the afd character of the transition.

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Section: Nmr Experiments At the High Temperature Phase Transition In ...supporting

confidence: 53%

Section: Nmr Experiments At the High Temperature Phase Transition In ...mentioning

confidence: 99%

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A microscopic model for the concentration dependence of the antiferrodistortive phase transition in mixed betaine phosphate/phosphite crystals

Braeter

Totz

Michel

1999

J. Phys.: Condens. Matter

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“…The result is shown in figure 8, where the points represent the experimental T C1 -data. The temperature given there will be calibrated more exactly by means of ultrasonic measurements on DBPI [14], which allow a precise determination of T C1 . From figure 8 it follows that the difference in T C1 -value between pure DBP and DBPI is only ≈7 K, indicating a slight deviation from the expected value of 10 K [1,2].…”

Section: 21mentioning

confidence: 99%

²H nuclear magnetic resonance studies on the deuteron dynamics in betaine phosphate/phosphite mixed crystals

Totz¹,

Braeter²,

Michel³

1999

J. Phys.: Condens. Matter

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One- and two-dimensional 2H NMR measurements on selected single crystals of deuterated betaine phosphate/phosphite mixed crystals (DBP1-xDBPIx) in the antiferrodistortive and paraelectric phases were performed in order to study the static and dynamic behaviour of the deuterium atoms in the hydrogen bridges and in the methylene groups. In the 2H nuclear magnetic resonance (NMR) spectra of the mixed crystals, it is possible to distinguish between DBP and DBPI molecules. Furthermore, for all deuterons the electric field gradient (EFG) tensors could be determined. A characteristic dependency of the high-temperature phase transition on the phosphite concentration x was derived from the changes of the one-dimensional 2H NMR spectra. Our suggested model, which describes this dependency qualitatively, underlines the antiferrodistortive character of this transition. Furthermore, from the line-shape variations, the occurrence of processes of exchange between several deuterons, including DBP and DBPI molecules, was concluded. The presence of exchange between different molecules in the chains was confirmed by means of analysing the cross-peaks of two-dimensional 2H NMR exchange experiments. The observation of this charge-transport process along the chains from the microscopic point of view is very important for the understanding of electrical conductivity processes in these crystals.

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Ultrasonic investigation of elastic phase transitions in betaine compounds

Samulionis

Banys

Völkel

2000

Journal of Alloys and Compounds

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Ultrasonic Anomalies in Deuterated Betaine Phosphite near the Ferroelectric Phase Transition

Cited by 3 publications

References 21 publications

A microscopic model for the concentration dependence of the antiferrodistortive phase transition in mixed betaine phosphate/phosphite crystals

A microscopic model for the concentration dependence of the antiferrodistortive phase transition in mixed betaine phosphate/phosphite crystals

²H nuclear magnetic resonance studies on the deuteron dynamics in betaine phosphate/phosphite mixed crystals

Ultrasonic investigation of elastic phase transitions in betaine compounds

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Ultrasonic Anomalies in Deuterated Betaine Phosphite near the Ferroelectric Phase Transition

Cited by 3 publications

References 21 publications

A microscopic model for the concentration dependence of the antiferrodistortive phase transition in mixed betaine phosphate/phosphite crystals

A microscopic model for the concentration dependence of the antiferrodistortive phase transition in mixed betaine phosphate/phosphite crystals

2H nuclear magnetic resonance studies on the deuteron dynamics in betaine phosphate/phosphite mixed crystals

Ultrasonic investigation of elastic phase transitions in betaine compounds

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Product

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²H nuclear magnetic resonance studies on the deuteron dynamics in betaine phosphate/phosphite mixed crystals