A COMPARATIVE STUDY OF THE DIELECTRIC BEHAVIOUR OF ICE IN WATER-CONTAINING SYSTEMS

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A COMPARATIVE STUDY OF THE DIELECTRIC BEHAVIOUR OF ICE IN WATER-CONTAINING

SYSTEMS

Polycarpos Pissis, L. Apekis, C. Christodoulides

To cite this version:

Polycarpos Pissis, L. Apekis, C. Christodoulides. A COMPARATIVE STUDY OF THE DIELEC-

TRIC BEHAVIOUR OF ICE IN WATER-CONTAINING SYSTEMS. Journal de Physique Colloques,

1987, 48 (C1), pp.C1-135-C1-141. �10.1051/jphyscol:1987120�. �jpa-00226265�

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JOURNAL DE PHYSIQUE

Colloque C1, suppl6ment a u

no 3,

Tome 48, mars 1987

A COMPARATIVE S T U D Y OF T H E DIELECTRIC BEHAVIOUR OF I C E I N WATER-CONTAINING SYSTEMS("

P. PISSIS, L. APEKLS a n d C. CHRISTODOULIDES

N a t i o n a l T e c h n i c a l U n i v e r s i t y o f A t h e n s , P h y s i c s D e p a r t m e n t , Z o g r a f o u Campus,

GR-157 73

A t h e n s , G r e e c e

RCs&.- La relaxation dielectrique dipolaire de la glace dans des systemes contenant de l'eau a GtB Ltudise par la msthode des thermocourants de dspolarisation (T.C.D.). Ces systsmes sont: glace polycristalline pure, Smulsions du type eau-dans- huile et du type huile-dans-eau gelses, solutions aqueuses de saccharides gelses, 6chantillons solides hydratss de saccharides, d'acides amincs et de protCines et feuilles de plantes. On a trouvs que les paramitres de relaxation diffgrent de fafon caractcristique pour les diffcrents systiimes Gtudigs. Les rcsultats expi5rimentaux sont discutez en termes de concentration de dgfauts d'origine physique dans les systsmes de la glace et de diffcrents modes de liaison de l'eau dans les matGriaux hy- drat&. Pour caracteriser l'stat physique de l'eau dans les systgmes la contenant, la mEthode T.C.D. s'est montrGe un outil trCs efficace.

Abstract.- The dipolar dielectric relaxation of ice in several water-containing systems has been studied by means of the thermally stimulated depolarisation (TSD) method. Thesesystems are: pure polycrystalline ice, frozen water-in-oil and oil-in- water emulsions, frozen aqueous solutions of saccharides, hydrated solid samples of

saccharides, aminoacids and proteins and plant leaves. The parameters descri-bingthe relaxation are in a characteristic way different for different systems. The results are discussed in terms of the concentration ofphysical defects in the ice systemsand the different binding modes of water in hydrated materials. The TSD method proves itself a powerful tool in characterizing the neighbourhood of reorientating watermo- lecules in water-containing systems.

1. Introduction

We report in this paper on the dielectric behaviour of ice in several water-containing systems studied by means of the thermally stimulated depolarisation (TSD) technique. These systems are: pure polycrystalline ice, frozen W/O and O/W

emulsions, frozen aqueous solutions of saccharides, hydrated solid samples of saccharides and proteins and plant leaves.

The paper has two objectives. The first is to contribute to a better under- standing of the dielectric properties of ice. We think that experiments on different ice systems can be very useful in checking the theories on the electrical and dielectric properties of ice. The second objective is related to the development in re- cent years of dielectric techniques into a powerful tool for the study of the binding modes of water in hydrated materials (irrotationall~ bound water, loosely bound wa-

ter, free water

n,~]).

Their use is based on the strong dipolar character of the water molecule and the dependence of the microdynamics of its reorientation in an ap- plied electric field on its neighbourhood. The characteristics of the dielectric relaxation which is attributed to reorientation of sorbed water molecules can then be

("work supported partly by the Greek Ministry of Research and Technology

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987120

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Ci-136 JOURNAL

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e x p e c t e d t o b e d i f f e r e n t t h a n t h o s e i n macroscopic p u r e w a t e r o r i c e and d i f f e r e n t f o r d i f f e r e n t b i n d i n g modes. I n f a c t , t h e spectrum o f d i e l e c t r i c r e l a x a t i o n t i m e s o f s o r b e d w a t e r m o l e c u l e s i s u s u a l l y b o t h a t t e m p e r a t u r e s above and below O0 C s i g n i f i - c a n t l y more complex t h a n t h a t of macroscopic w a t e r o r i c e and i s a l s o s h i f t e d t o l a r - g e r t i m e s . However, j u s t b e c a u s e of t h i s c o m p l e x i t y , t h e i n t e r p r e t a t i o n of t h e r e - s u l t s o f d i e l e c t r i c measurements i n h y d r a t e d m a t e r i a l s i n t e r m s o f d i f f e r e n t b i n d i n g modes o f w a t e r m o l e c u l e s i s s t i l l c o n t r o v e r s i a l and v e r y o f t e n s i m i l a r e x p e r i m e n t a l r e s u l t s have been i n t e r p r e t e d i n q u i t e d i f f e r e n t ways [3]. By s t u d y i n g t h e c h a r a c t e - r i s t i c s of t h e d i e l e c t r i c r e l a x a t i o n d u e t o r e o r i e n t a t i o n o f w a t e r m o l e c u l e s i n ma- c r o s c o p i c i c e and i n i c e i n s e v e r a l w a t e r - c o n t a i n i n g systems we hope t o c o n t r i b u t e t o t h e c l a r i f i c a t i o n o f t h i s problem.

2. E x p e r i m e n t a l .

The TSD method i s a s f o l l o w s [ 4 ] . The sample i s p o l a r i s e d by a n a p p l i e d e l e c t r i c f i e l d Ep. T h i s p o l a r i s a t i o n i s s u b s e q u e n t l y f r o z e n i n by c o o l i n g t h e sample down t o a t e m p e r a t u r e To s u f f i c i e n t l y low t o p r e v e n t d e p o l a r i s a t i o n by t h e r m a l energy. The f i e l d i s t h e n s w i t c h e d o f f and t h e sample i s warmed up a t a c o n s t a n t r a t e b , w h i l e t h e d e p o l a r i s a t i o n c u r r e n t , a s t h e d i p o l e s r e l a x , i s d e t e c t e d by an e l e c t r o m e t e r . Thus f o r each p o l a r i s a t i o n mechanism a n i n h e r e n t c u r r e n t peak c a n b e d e t e c t e d . A major f e a t u r e o f t h e TSD method, which makes i t a t t r a c t i v e f o r o u r p u r p o s e s , i s t h a t i t o f f e r s t h e p o s s i b i l i t y t o e x p e r i m e n t a l l y r e s o l v e r e l a x a t i o n p r o c e s s e s a r i s i n g from s e t s of d i p o l e s w i t h s l i g h t l y d i f f e r e n t r e l a x a t i o n t i m e s .

I n t h e c a s e o f a s i n g l e r e l a x a t i o n p r o c e s s o b e y i n g t h e A r r h e n i u s e q u a t i o n

t h e d e p o l a r i s a t i o n c u r r e n t d e n s i t y J ( T ) i s g i v e n by t h e e q u a t i o n

J (T) =

- Po

exp (-W/kT) exp

To [- -j

exp(-W/kTP) dT'

1

'0

where r i s t h e r e l a x a t i o n t i m e , W t h e a c t i v a t i o n energy o f t h e r e l a x a t i o n , ⁱ t h e p r e - e x p o n e n t i a l f a c t o r , T t h e a b s o l u t e t e m p e r a t u r e , k Boltzmann's c o n s t a n t , 2nd PO t h e i n i t i a l p o l a r i s a t i o n . The a n a l y s i s o f t h e s h a p e of t h i s c u r v e makes i t p o s s i b l e t o o b t a i n t h e a c t i v a t i o n energy W , t h e p r e - e x p o n e n t i a l f a c t o r r 0 , and t h e c o n t r i b u - t i o n AE of a peak t o t h e s t a t i c p e r m i t t i v i t y E3-51.

We used a c r y o s t a t f o r measurements i n t h e t e m p e r a t u r e r a n g e 77-300K. D e t a i l s o f t h e e x p e r i m e n t a l a p p a r a t u s and t h e p r e p a r a t i o n o f t h e samples have b e e n g i v e n i n p r e v i o u s p u b l i c a t i o n s [6-111.

3. Results a n d D i s c u s s i o n .

TSD measurements on macroscopic p o l y c r y s t a l l i n e p u r e i c e show two predominant peaks a t a b o u t 120 and 220K. The low-temperature TSD peak a t a b o u t 120K h a s been a t t r i - b u t e d t o t h e r e o r i e n t a t i o n of w a t e r m o l e c u l e s i n i c e [63 and t h e h i g h - t e m p e r a t u r e peak a t a b o u t 220K t o s p a c e c h a r g e r e l a x a t i o n 1121. S i n c e we a r e i n t e r e s t e d i n t h e d i p o l a r d i e l e c t r i c r e l a x a t i o n o f w a t e r m o l e c u l e s , we c o n f i n e d o u r s t u d i e s t o t h e l o w - t e m p e r a t u r e r a n g e o f 77-170K. F i g u r e 1 shows t h e peak a t 120K. D e t a i l e d e x p e r i - m e n t a l s t u d i e s r e p o r t e d a t t h i s Conference by D r . Apekis show t h a t t h e peak i s n o t s i n g l e . The main r e l a x a t i o n mechanism c o n t r i b u t i n g t o i t i s c h a r a c t e r i z e d by a n a r - row c o n t i n u o u s d i s t r i b u t i o n of r e l a x a t i o n t i m e s around a mean v a l u e . The mean v a l u e of t h e a c t i v a t i o n e n e r g y i s i n t h e r a n g e of 0.25-0.30 eV, depending on t h e method o f e v a l u a t i o n . The r e s u l t s o f TSD measurements on macroscopic p o l y c r y s t a l l i n e p u r e i c e h a v e been e x p l a i n e d a t t h e m o l e c u l a r l e v e l by e x t e n d i n g J a c c a r d and G r z n i c h e r ' s t h e - o r y of t h e d i e l e c t r i c p r o p e r t i e s of i c e E l 3 1 t o low-temperature TSD measurements [ 1 4 ] . I n t h i s e x t e n s i o n t h e r e o r i e n t a t i o n o f w a t e r m o l e c u l e s i s r e a l i z e d b y t h e mo- t i o n o f Bjerrum D and L d e f e c t s .

I n a l l t h e systems s t u d i e d a TSD band was o b s e r v e d i n t h e t e m p r a t u r e r a n g e 77- 170K. The p o s i t i o n , t h e s h a p e and t h e magnitude o f t h e band a s w e l l a s t h e dependence o f t h e s e q u a n t i t i e s on t h e w a t e r c o n t e n t a r e i n a c h a r a c t e r i s t i c way d i f f e r e n t f o r d i f f e r e n t systems. Our measurements p r o v i d e d s e v e r a l i n d i c a t i o n s s u p p o r t i n g t h e h y p o t h e s i s t h a t t h e band i s due t o r e o r i e n t a t i o n of w a t e r m o l e c u l e s :

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i ) The d e p o l a r i s a t i o n charge obtained from t h e a r e a u n d e r t h e TSD band was found t o i n c r e a s e f o r t h e same system w i t h i n c r e a s i n g w a t e r c o n t e n t . I n t h e c a s e of hydrated compressed p e l l e t s of s a c c h a r i d e s and p r o t e i n s t h e low-temperature TSD band appears o n l y f o r water c o n t e n t s h h i g h e r t h a n a c r i t i c a l h y d r a t i o n l e v e l hc, which i s d i f f e r e n t f o r d i f f e r e n t m a t e r i a l s . For h l a r g e r t h a n hc t h e d e p o l a r i s a t i o n charge i n c r e a s e s l i n e a r l y w i t h i n c r e a s i n g h ( F i g . 2 ) . I n t h e c a s e of f r o z e n w a t e r - i n - o i l e- mulsions t h e i n c r e a s e of t h e d e p o l a r i s a t i o n charge w i t h i n c r e a s i n g water c o n t e n t i s not l i n e a r f o r reason we can w e l l understand [15].

i i ) The p o s i t i o n and t h e shape of t h e band were found t o b e , f o r t h e same Sys- tem and t h e same w a t e r c o n t e n t , independent of t h e p o l a r i s i n g f i e l d , w h i l e t h e depo- l a r i s a t i o n charge was found t o i n c r e a s e l i n e a r l y w i t h i n c r e a s i n g p o l a r i s i n g f i e l d . An example i s shown i n f i g u r e 3. These r e s u l t s i n d i c a t e t h a t t h e band i s due t o d i p o l a r r a t h e r t h a n space charge r e l a x a t i o n [ 5 j , i n c o n s i s t e n c y w i t h t h e h y p o t h e s i s t h a t t h e r e o r i e n t a t i o n of water molecules i s i t s cause.

i i i ) We prepared and s t u d i e d i n some c a s e s systems with H 0 being r e p l a c e d by D20. For each system, and f o r t h e same water c o n t e n t , t h e low-temperature TSD bands 2 i n t h e H20- and D20- systems w e r e s i m i l a r i n s h a p e , t h e band i n t h e D20-system being s h i f t e d by 4K towards h i g h e r temperatures. Also i n pure H20 and D20 i c e t h e low- temperature TSD peaks a r e s i m i l a r i n shape, t h e peak temperature TN being 4K h i g h e r i n heavy i c e . An example i s shown i n f i g u r e 4.

Regarding t h e shape of t h e low-temperature TSD band, t h r e e d i f f e r e n t t y p e s of behaviour have been observed. Type S i s t h a t of an approximately s i n g l e peak ( t o t h e same degree a s t h a t i n macroscopic p o l y c r y s t a l l i n e p u r e i c e ) . Frozen w a t e r - i n - o i l e- mulsions and f r o z e n c o n c e n t r a t e d s o l u t i o n s ( ~ 2 0 . 7 m o l l l i t r e ) of t h e monosaccharides g l u c o s e , mannose and g a l a c t o s e show t h i s type of behaviour. The peak temperature TM i s h i g h e r than i n macroscopic p o l y c r y s t a l l i n e pure i c e . Type M i s t h a t of a peak which i s both s i g n i f i c a n t l y broader and l o c a t e d a t a h i g h e r temperature t h a n t h e peak

i n macroscopic p o l y c r y s t a l l i n e pure i c e . D i l u t e s o l u t i o n s ( ~ 5 0 . 7 m o l l l i t r e ) of t h e monosaccharides g l u c o s e , mannose and g a l a c t o s e , hydrated compressed p e l l e t s of t h e s a c c h a r i d e s g a l a c t o s e and maltose monohydrate, t h e p o l y s a c c h a r i d e c e l l u l o s e and t h e p r o t e i n c a s e i n and p l a n t l e a v e s show t h i s t y p e of behaviour. F i n a l l y , t y p e D i s t h a t of a double peak, t h e f i r s t peak b e i n g l o c a t e d a t t h e same temperature a s t h e peak i n macroscopic p o l y c r y s t a l l i n e pure i c e and t h e second peak a t a h i g h e r temperature.

Frozen o i l - i n - w a t e r emulsions and f r o z e n s o l u t i o n s of t h e s a c c h a r i d e s a r a b i n o s e , r i - bose, m a l t o s e , l a c t o s e and c e l l o b i o s e show t h i s t y p e of behaviour.

I n concentrated s o l u t i o n s ( ~ 1 0 . 7 m o l l l i t r e ) of t h e monosaccharides g l u c o s e , mannose and g a l a c t o s e , t h e temperature of t h e approximately s i n g l e peak i s about130K and t h e (mean) a c t i v a t i o n energy W about 0.34 eV. W e have good reasons t o b e l i e v e t h a t t h e peak i s due t o t h e r e o r i e n t a t i o n of w a t e r molecules, which a r e i n f l u e n c e d by t h e presence of t h e s o l u t e molecules [3,93.

I n d i s p e r s i o n s of i c e m i c r o c r y s t a l s i n o i l t h e peak temperature TM and t h e mean a c t i v a t i o n energy W depend on t h e volume f r a c t i o n Q, of t h e d i s p e r s e d w a t e r phase. For

@ = 0 . 4 0 , f o r example, we found T = 140K and Wz0.34 eV. The p r o p e r t i e s of t h e peak were found t o change w i t h time, ! h e n a f t e r f r e e z i n g a t T f r t h e emulsion was preserved a t a c o n s t a n t temperature between Tfr and O°C [7}. An example i s shown i n f i g u r e 5.

A d e t a i l e d s t u d y by means o f peak r e s o l v i n g experimental t e c h n i q u e s o f f e r e d by t h e TSD method 19-11] shows t h a t t h e peak i s c h a r a c t e r i z e d by a continuous d i s t r i b u t i o n of r e l a x a t i o n times w i t h b o t h t h e a c t i v a t i o n energy W and t h e pre-exponential f a c t o r

T~ being d i s t r i b u t e d . It shows f u r t h e r t h a t t h e d i e l e c t r i c behaviour of d i s p e r s e d i c e m i c r o c r y s t a l s resembles s t r o n g l y i n some a s p e c t s (such a s t h e v a l u e s and t h e tem- p e r a t u r e dependence of t h e a c t i v a t i o n energy W and t h e change of t h e d i e l e c t r i c pro- p e r t i e s w i t h time) t h a t of macroscopic Hz-doped i c e [16] and i c e samples w i t h high c o n c e n t r a t i o n s of c r y s t a l i n p e r f e c t i o n s 117,181. A p o s s i b l e e x p l a n a t i o n of t h e l a r - g e r r e l a x a t i o n times and t h e h i g h e r a c t i v a t i o n energy i n a l l t h e s e i c e systems, a s compared t o macroscopic p o l y c r y s t a l l i n e pure i c e , i s t h a t t h e motion of o r i e n t a t i o n a l D and L d e f e c t s i s hampered by t h e h i g h c o n c e n t r a t i o n of p h y s i c a l d e f e c t s .

I n d i l u t e s o l u t i o n s ( ~ 5 0 . 7 m o l l l i t r e ) of t h e monosaccharides glucose, mannose and g a l a c t o s e , t h e broad peak has been s t u d i e d i n d e t a i l . By v a r y i n g t h e s o l u t e con- c e n t r a t i o n over a wide range and mainly by u s i n g s e v e r a l experimental techniques o f - f e r e d by t h e TSD method, such a s t h e technique of v a r y i n g t h e p o l a r i s a t i o n temperatu- r e Tp, t h e technique of i n c r e a s i n g t h e r e s o l v i n g power of t h e TSD method by lowering

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Fig.1.- The low-temperature TSD peak of Fig.2.- Linear correlation between the macroscopic polycrystalline pure ice. contribution As of the peak in hydrated

maltose to the static permittivity and its water content h.

Fig.3.- Linear correlation betweenpeak's amplitude I, and polarizing field E for the peak of Olea europaea leaves.

Fig.4.- TSD bands for 0.001M maltose solution in H20 (-) and D 0 (---).

2

the heating rate b, the partial heating technique and the thermal sampling technique, we could show that the peak is multiple and the corresponding relaxation process con- tinuously distributed, with both the activation energy W and the pre-exponential fa-

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c t o r r 0 b e i n g d i s t r i b u t e d parameters. A l i n e a r r a l a t i o n s h i p e x i s t s between W and lnT0, t h e so-called compensation law ( F i g . 6 ) . The r e s u l t s show t h a t i n t h e s e solu- t i o n s t h e r e i s a continuous t r a n s i t i o n from h y d r a t i o n t o f r e e w a t e r molecules. On t h e b a s e of t h e s p e c i f i c h y d r a t i o n model [lg] t h i s r e s u l t s f r o b t h e f a c t t h a t gluco- s e , mannose and g a l a c t o s e can f i t w e l l i n t o t h e i c e s t r u c t u r e .

The r e s u l t s i n hydrated compressed p e l l e t s of g a l a c t o s e , m a l t o s e , c e l l u l o s e a n d c a s e i n make i t r e a s o n a b l e t o a c c e p t t h a t t h e broad peak, which appears o n l y f o r w a t e r c o n t e n t s h h i g h e r t h a n a c r i t i c a l h y d r a t i o n l e v e l and t h e n i n c r e a s e s l i n e a r l y w i t h i n c r e a s i n g h , i s due t o t h e r e o r i e n t a t i o n of l o o s e l y bound w a t e r molecules. T h e c r i - t i c a l h y d r a t i o n l e v e l corresponds t o t h e f r a c t i o n of w a t e r molecules t h a t a r e t i g t h - l y ( i r r o t a t i o n a l l y ) bound. I t s e v a l u a t i o n i s u s e f u l i n checking models p r e d i c t i n g t h e number of h y d r a t i o n s i t e s i n t h e molecular s t r u c t u r e . The r e s u l t s show t h a t t h e peak i s c h a r a c t e r i z e d by a continuous d i s t r i b u t i o n of r e l a x a t i o n times w i t h t h e a c t i - v a t i o n energy W b e i n g a d i s t r i b u t e d parameter ( F i g . 7 ) . The mean v a l u e s of T and W a r e ( s l i g h t l y ) d i f f e r e n t f o r d i f f e r e n t systems and d i f f e r e n t w a t e r c o n t e n t s b u t a l - ways h i g h e r t h a n t h e corresponding v a l u e s f o r macroscopic p o l y c r y s t a l l i n e p u r e i c e . The r e s u l t s may be e x p l a i n e d by t h e h y p o t h e s i s of t h e e x i s t e n c e of a v a r i e t y of s t r u c t u r e s of modified water. An a l t e r n a t i v e e x p l a n a t i o n i s t h a t t h e continuous di- s t r i b u t i o n of r e l a x a t i o n times a r i s e s from a d i s t r i b u t i o n of s i z e s of w a t e r c l u s t e r s .

Measurements i n p l a n t l e a v e s show s i m i l a r r e s u l t s t o t h o s e i n hydrated saccha- r i d e s and p r o t e i n s , w i t h t h e mean v a l u e s of T and B b e i n g even h i g h e r d e s p i t e t h e i r l a r g e r w a t e r c o n t e n t s .

The double peak i n f r o z e n oil-in-water emulsions and i n f r o z e n aqueous solu- t i o n s of t h e s a c c h a r i d e s a r a b i n o s e , r i b o s e , m a l t o s e , l a c t o s e and c e l l o b i o s e could b e e x p e r i m e n t a l l y resolved i n t o two peaks (Fig.8) corresponding t o two d i s c r e t e k i n d s of w a t e r molecules, namely f r e e and h y d r a t i o n molecules. These s a c c h a r i d e s cannot f i t w e l l i n t o t h e i c e s t r u c t r e and t h u s a c t a s s t r u c t u r e b r e a k e r s .

Fig.5.- Evolution w i t h time of t h e TSD Fig.6.- L i n e a r r e l a t i o n s h i p between W peak i n an i c e emulsion w i t h 0 = 0 . 4 0 : A , and of t h e thermal sampling r e s - immediately a f t e r f r e e z i n g ; B, a f t e r 1 ponses l s o l a t e d i n t h e TSD band of t h e hour p r e s e r v a t i o n a t -2'~. 0.1M mannose s o l u t i o n .

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CI-140

JOURNAL DE PHYSIQUE

Fig.7.- Peak temperature T (6) and acti- Fig.8.- Analysis of the TSD band in a vation energy W(o) of the ?herma1 sam- frozen oil-in-water with 0 ~ 0 . 4 0 into pling responses isolated in the TSD band two discrete peaks.

of hydrated cellulose with h = 20.4% as a function of the polarisation temperature T

P '

References

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COMMENTS

In our calorimetric experiment, we found a very slow change of the property of ice sample around 100 K that took days for completion (Keda, Matsuo and Suga, J. Phys.

Chem. Solids,

9,

1165 (1982) and references theirin). Since the TSD experiment can also detect slow changes, it should be interesting to do the TSD measurement on the ice annealed around 100 K in the electric field.

Answer :

In fact, the TSD technique is very suitable in studying slow changes of properties of materials, since it corresponds to frequencies in the range of 10-I

-

^Hz.

The TSD technique has already been used in the study of slow phase transitions in polymers and in other materials too

.

We intend to study the changes observed in ice by calorimetric measurements around 100 K by using the TSD technique in its usual form, as well as without the application of an electric field. We think that it is interesting to see if the application of a dc field has any influence on the observed changes.

VANDERSCHUEREN, J. and GASIOT, J., in Thermally Stimulated Relaxation in Solids, P. Braunlich ed. (Springer Verlag, Berlin) 1979.