Search for memory and return to disorder in potassium-lithium tantalate crystals

Abstract

Return to disorder, and less frequently memory, have been demonstrated in various disordered materials. In order to find the conditions necessary for the observation of these effects, the evolution of the real part ´ of the dielectric constant of two disordered paraelectric crystals K1-x Lix TaO3 (KLT) has been extensively studied by the means of the capacitance C (T , t ) around the beginning and the end of a temperature plateau. The return to disorder and memory effects have not been seen in KTL, in contrast to what was recently observed in disordered ferroelectric crystals KTa1-y Nby O3 of a similar family. The variations dC = P (T 0 , t 0 ) dT + Q (T 0 , t 0 ) dt in the vicinity of the point (T 0 , t 0 ) are split into a contribution depending on temperature only and an isothermal contribution only depending on time. All the results of such an analysis of the features observed in KLT can be explained by the domain wall model in its original form.

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

“…The method was first applied to look for return-to-disorder KLT crystals. In this case the results were clearly negative: the searched effect is absent in KLT [14]. In the present study the method is applied to KTN crystals in the modified following way.…”

“…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).…”

“…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.…”

“…Method. -The principle of our method has been described elsewhere [14]. It consists in the study of differential variations of the complex capacitance C(T, t) in the vicinity of some remarkable point (T 0 , t 0 ) in the(T, t) space.…”

“…For this purpose, we first recall the results of experiments performed on KLT, another disordered dielectric [14]. In this material, two results were obtained for the real part of the capacitance (the loss is too weak to be measured): the partial derivatives of C (T, t pl ) with respect to temperature for T = T pl were found to be equal for dT positive and dT negative and the common value does not depend on the plateau duration t pl .…”