Dielectric secondary relaxation of water in aqueous binary glass-formers

Sjöström, Johan; Mattsson, Johan; Bergman, Rikard; Johansson, Erik; Josefsson, Karin; Svantesson, David; Swenson, Jan

doi:10.1039/c001275k

Cited by 47 publications

(67 citation statements)

References 38 publications

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“…16. Thus, the absorption of water molecules by a crystal surface can affect the dielectric constant of the crystal and contribute to dielectric peak as reported in the literature [49][50][51]. Beyond 145°C, the title crystal shows normal behavior and dielectric constant increases with temperature as observed in various polar materials [52].…”

Section: Ft-ir Analysismentioning

confidence: 89%

Structural, optical and dielectric studies of lithium sulphate monohydrate single crystals

Najar

Vakil

Want

2017

Materials Science-Poland

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Optical, dielectric, and thermal properties of lithium sulphate monohydrate crystals grown by slow evaporation method have been studied. The crystal structure was resolved by direct methods using single crystal X-ray diffraction data collected at room temperature and refined by full-matrix least-squares procedures to a final R-value of 0.0174. Plasma energy, Penn gap, Fermi energy and electronic polarizability of the grown crystal were calculated from single crystal XRD data. The electronic polarizability of lithium sulfate monohydrate was also calculated and compared with the theoretical data using Clausius-Mossotti equation. Optical band gap calculated from optical data for the grown crystal is 4.49 eV. Fourier Transform Infrared Spectroscopy study confirmed the presence of water in the crystal structure. The AC conductivity, dielectric constant and dielectric loss of the grown crystal were systemically investigated, showing a peak at about 130°C which could be attributed to the water molecules in the crystal structure. The anomalous dielectric properties shown by the crystal have been correlated with its thermal behavior. The title crystal obeys Jonscher's power law relation; σ(ω) = σ o + Aω s , with temperature dependent exponent s < 1. The activation energy calculated for the material is 0.24 eV and suggests protonic conduction by hopping mechanism in addition to cationic conduction by lithium ions. The micro-indentation study was also carried out which revealed that the crystal belongs to a category of soft materials.

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Section: Ft-ir Analysismentioning

confidence: 89%

Structural, optical and dielectric studies of lithium sulphate monohydrate single crystals

Najar

Vakil

Want

2017

Materials Science-Poland

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“…Upon increasing water content the T g of PG decreases slowly, but steadily, until partial crystallisation of water occurs at about 60 wt.% water. 3 On the other hand, for PGME the concentration dependence of T g exhibits an anomalous behavior, with a maximum of 169 K at 55 wt.% water. 3 Clearly, the hydrogen bonds in water are affecting the viscosity and glass transition related dynamics in these systems very differently.…”

Section: Introductionmentioning

confidence: 99%

“…3 On the other hand, for PGME the concentration dependence of T g exhibits an anomalous behavior, with a maximum of 169 K at 55 wt.% water. 3 Clearly, the hydrogen bonds in water are affecting the viscosity and glass transition related dynamics in these systems very differently. In the case of the PG-water system infinitely long chains or clusters of hydrogen bonded molecules can be formed at all water concentrations, and therefore it is likely that water does not substantially affect the dynamics of the PG molecules.…”

Section: Introductionmentioning

confidence: 99%

Anomalous dynamics of aqueous solutions of di-propylene glycol methylether confined in MCM-41 by quasielastic neutron scattering

Swenson

Elamin

Chen

et al. 2014

The Journal of Chemical Physics

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The molecular dynamics of solutions of di-propylene glycol methylether (2PGME) and H 2 O (or D 2 O) confined in 28 Å pores of MCM-41 have been studied by quasielastic neutron scattering and differential scanning calorimetry over the concentration range 0-90 wt.% water. This system is of particular interest due to its pronounced non-monotonic concentration dependent dynamics of 2PGME in the corresponding bulk system, showing the important role of hydrogen bonding for the dynamics. In this study we have elucidated how this non-monotonic concentration dependence is affected by the confined geometry. The results show that this behaviour is maintained in the confinement, but the slowest diffusive dynamics of 2PGME is now observed at a considerably higher water concentration; at 75 wt.% water in MCM-41 compared to 30 wt.% water in the corresponding bulk system. This difference can be explained by an improper mixing of the two confined liquids. The results suggest that water up to a concentration of about 20 wt.% is used to hydrate the hydrophilic hydroxyl surface groups of the silica pores, and that it is only at higher water contents the water becomes partly mixed with 2PGME. Hence, due to this partial micro-phase separation of the two liquids larger, and thereby slower relaxing, structural entities of hydrogen bonded water and 2PGME molecules can only be formed at higher water contents than in the bulk system. However, the Q-dependence is unchanged with confinement, showing that the nature of the molecular motions is preserved. Thus, there is no indication of localization of the dynamics at length scales of less than 20 Å. The dynamics of both water and 2PGME is strongly dominated by translational diffusion at a temperature of 280 K.

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“…Thus, the water molecules absorbed to the crystal boundary of a compound could impose great impact on the dielectric property and may contribute to the anomalous dielectric peak as also reported in the literature. [21][22][23] The dependence of dielectric loss (tan) of GTF heptahydrate crystals also exhibit a similar type of variation with temperature at different frequencies showing a peak at around 90 C as shown in Fig. 6.…”

Section: Dielectric Characteristics Of Gtf Heptahydrate Crystalsmentioning

confidence: 80%

Dielectric and conducting behavior of gadolinium–terbium fumarate heptahydrate crystals

Shah

Want

2015

J. Adv. Dielect.

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Gadolinium-terbium fumarate heptahydrate crystals were grown in silica gel by using single gel diffusion technique. The crystals were characterized by different physico-chemical techniques of characterization. Powder X-ray diffraction results showed that the grown material is purely crystalline in nature. Elemental analyses suggested the chemical formula of the compound to be Gd Tb (C 4 H 2 O 4 Þ 3 Á 7H 2 O. Energy dispersive X-ray analysis confirmed the presence of Gd and Tb in the title compound. The dielectric and conductivity studies of the grown compound were carried as function of frequency of applied field and the temperature. The grown material showed a dielectric anomaly which was correlated with its thermal behavior. The ac conductivity of the material showed Jonscher's power law behavior: ð!Þ ¼ o þ A! s , with a temperature-dependent power exponent s (<1). The conductivity was found to be a function of temperature and frequency.

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Dielectric secondary relaxation of water in aqueous binary glass-formers

Cited by 47 publications

References 38 publications

Structural, optical and dielectric studies of lithium sulphate monohydrate single crystals

Structural, optical and dielectric studies of lithium sulphate monohydrate single crystals

Anomalous dynamics of aqueous solutions of di-propylene glycol methylether confined in MCM-41 by quasielastic neutron scattering

Dielectric and conducting behavior of gadolinium–terbium fumarate heptahydrate crystals

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