Non ergodic aging in potassium niobo-tantalate crystals

Doussineau, P.; Lacerda-Arôso, T. de; Levelut, A.

doi:10.1007/s100510070203

Cited by 6 publications

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“…-Aging is a widespread phenomenon. Noticed on the elastic compliance of polymers a long time ago [1], it has also been observed in many solids: on the magnetic susceptibility χ of spin-glasses (SG) [2-5], on the elastic constant c and on the dielectric constant ε of disordered dielectrics [6][7][8]. Aging is said to occur when the evolution is nonstationary and depends on the thermal history; it may lead to ergodicity breaking [7].…”

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Aging, return to disorder and derivability breaking in potassium niobo-tantalate crystals

Doussineau¹,

Levelut²

2000

Europhys. Lett.

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In the ferroelectric phase of two KTa1−xNbxO3 (x = 0.022 and x = 0.027) samples, we have measured the variation of the real and imaginary parts of the complex dielectric constant ε just after an isothermal evolution of duration t pl at the temperature T pl (plateau). We have found that the temperature derivative dε dT (T, t pl ) has not the same value for T = T pl +0 and T = T pl − 0 if t pl is not zero; this means that ε(T, t pl ) is not derivable with respect to T . Return to disorder is carefully defined. Its occurrence after a temperature plateau at T pl has been studied for fixed T pl as a function of t pl and of measurement frequency.Introduction. -Aging is a widespread phenomenon. Noticed on the elastic compliance of polymers a long time ago [1], it has also been observed in many solids: on the magnetic susceptibility χ of spin-glasses (SG) [2-5], on the elastic constant c and on the dielectric constant ε of disordered dielectrics [6][7][8]. Aging is said to occur when the evolution is nonstationary and depends on the thermal history; it may lead to ergodicity breaking [7]. This is a consequence of disorder and frustration.Recently, a surprising effect was observed in some materials after isothermal aging at the fixed temperature T pl (or plateau). Aging manifests itself by the decrease of some susceptibility (indeed, its real part and its imaginary part). This evolution tends necessarily towards more stability and thus more order. It may happen that upon cooling at the end of the plateau an immediate increase (generally of the imaginary part) is observed, thus indicating some return to disorder, although temperature is lowered. A memory effect is often associated with return to disorder [9][10][11].Return to disorder was observed in various compounds: in the ferroelectric lock-in phase of Rb 2 ZnCl 4 [12], in the SG phase of CdCr 1.7 In 0.3 S 4 [9] and in Cu:Mn [9, 10] which is a metallic SG, in the two phases (SG and ferromagnetic) of CdCr 1.9 In 0.1 S 4 [13], in the disordered dielectric KTa 1−x Nb x O 3 (KTN) [11] but not in K 1−y Li y TaO 3 (KLT) [14], which is also a disordered dielectric.In this letter, we present a precise definition of return to disorder and we report new dielectric measurements performed just at the end of isothermal aging. They provide quantitative data on two types of results: i) the derivatives of the complex dielectric constant with respect ( * ) Associated with the Centre National de la Recherche Scientifique (UMR 7603).

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Aging, return to disorder and derivability breaking in potassium niobo-tantalate crystals

Doussineau¹,

Levelut²

2000

Europhys. Lett.

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“…As a consequence, at fixed temperature they relax slowly towards a more ordered state; this is aging. Aging has been observed in polymers [1], spin glasses [2][3][4], supercooled liquids [5], disordered dielectrics [6][7][8][9][10], relaxor ferroelectrics [11] and colloidal glasses [12,13]. Some other phenomena are commonly associated with aging.…”

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confidence: 99%

“…In this paper we focus our attention on the behaviour of potassium niobo-tantalate KTa 1−y Nb y O 3 (KTN) crystals. At low temperatures, KTN crystals are in a disordered (because of the randomly substituted niobium atoms) ferroelectric phase and they show effective ergodicity breaking, rejuvenation and memory [10,16]. In another neighbouring family of disordered dielectrics, the potassium-lithium tantalate K 1−x Li x TaO 3 (KLT) crystals, which are in a paraelectric phase at low temperatures, effective ergodicity breaking was observed but neither rejuvenation nor memory [7,20].…”

Section: Introductionmentioning

confidence: 99%

“…In another neighbouring family of disordered dielectrics, the potassium-lithium tantalate K 1−x Li x TaO 3 (KLT) crystals, which are in a paraelectric phase at low temperatures, effective ergodicity breaking was observed but neither rejuvenation nor memory [7,20]. It is worth noticing that all the features observed in KLT are nearly independent of frequency [7], specially at low temperatures while they appear frequency dependent in KTN [10].…”

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confidence: 99%

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Aging and other related phenomena in potassium niobo-tantalate crystals studied through the frequency dependence of their dielectric constant

Doussineau

Lacerda-Arôso

Levelut

2001

J. Phys.: Condens. Matter

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We report on dielectric measurements in the frequency range from 1 to 1000 kHz in two disordered ferroelectric KTa 1−y Nb y O 3 (KTN) crystals (y ∼ = 0.02). We have studied the frequency dependence of the dielectric constant (real and imaginary parts) during several thermal evolutions: isothermal aging, rejuvenation by cooling or heating after a temperature plateau, memory. In every case the frequency dependence is well described by a power law. The temperature and plateau duration dependences of the exponents have been studied. We give a description of our results within a model where the variations of the dielectric constant are attributed to the motion (growth and reconformation) of ferroelectric domain walls. In particular we are able to explain the identity of the exponents of the frequency power law dependence of memory and isothermal aging.

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“…This kind of reversibility after irreversible evolution allows to use exactly the same sample in a series of experiments, all starting from the same state. Among this type of materials are structural glasses [2], spin-glasses [3][4][5] and disordered dielectrics [6][7][8][9].…”

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Effect of the biasing electric field on aging in potassium niobo-tantalate crystals

Doussineau¹,

Levelut²

2001

Europhys. Lett.

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Aging in the disordered ferroelectric potassium niobo-tantalate has been studied by measuring the real and imaginary parts of the dielectric constant at various frequencies when a biasing electric field is applied. It is found that rejuvenation and memory effects can be induced by the field. The effects of temperature and field are compared and the results are discussed in terms of a model which attributes the time-dependent part of the dielectric constant to growth and reconformation of the polarization domain walls.

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Non ergodic aging in potassium niobo-tantalate crystals

Abstract: PACS. 77.22.Gm Dielectric loss and relaxation – 78.30.Ly Disordered solids,

Cited by 6 publications

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Aging, return to disorder and derivability breaking in potassium niobo-tantalate crystals

Aging, return to disorder and derivability breaking in potassium niobo-tantalate crystals

Aging and other related phenomena in potassium niobo-tantalate crystals studied through the frequency dependence of their dielectric constant

Effect of the biasing electric field on aging in potassium niobo-tantalate crystals

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