Untersuchungen zur Fehlordnung von NH4 Cl-Kristallen

Klein

1986

phys. stat. sol. (a)

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Results of thermally stimulated current measurements of contacted and insulated, undoped and Ni doped NH4Cl and current measurements are described. Based on a quantitative analysis of the data of the insulated crystals it is shown that the crystals are polarized in the first place by blocked mobile point defects, anion vacancies in undoped and cation vacancies in doped crystals, that the dynamics of the polarization is determined by the bulk conductivity which exceeds by more than an order of magnitude the conductivity of crystals with contacts etc. Besides that, according to circumstances, there are however still other polarization effects caused by the point defect polarization itself and by all kind of surface processes.

Section: Conduction Measurementssupporting

confidence: 85%

“…(2.13) in [ll]). By doping NH,C1 with NiC1, o is increased [5]. Consequently the position of the SP peak should be shifted to lower temperatures, as observed (Table 1).…”

Section: The Figures Insupporting

confidence: 55%

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Conductivity and Polarization of NH4Cl between 150 and 500 K

Klein

1986

phys. stat. sol. (a)

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“…A practical criterion for the correctness of such an interpretation is e. g. the agreement between the value of the activation energy of motion determined from conductivity data and that determined from initial rise data. An agreement of this kind was found for CdF, [2] and for NH,C1 [9].…”

supporting

confidence: 67%

Investigation of the Space-Charge Formation in Polar Crystals by Means of Thermal Stimulated Current Measurements

1976

J. Phys. Colloques

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Rksum6. -Une analyse des conditions de mesures TSD et de quelques resultats experimentaux est presentee, qui montre que, sous des conditions propices, on peut mesurer une vitesse de depolarisation non perturbke ou un voltage de polarisation en circuit ouvert. I1 est de plus demontrk que l'on peut obtenir B partir de ces mesures le nombre des defauts et la chute de potentiel due aux defauts qui forment la charge spatiale. Cela rend possible la determination, au moins approximative, de la repartition initiale des charges dans l'espace B partir des donnees TSD.Abstract. -An analysis of the conditions of TSD-measurements and of some experimental results are presented which show, that given proper conditions, either the unperturbed depolarisation rate or an open circuit polarisation voltage can be measured. It is further shown, that from these measurements the number of defects and the potential drop caused by the defects forming the space charge can be obtained. This makes is possible to determine from the TSD data, approximative~ at least, the initial space charge distribution.

“…This was Paper 104 presented at the Dallas, Texas, Meeting of the Society, Oct. [5][6][7][8][9]1975. Any discussion of this paper will appear in a Discussion Section to be published in the June 1977 JOURNAL.…”

Section: Discussionmentioning

confidence: 99%

On the Maximum Position of Thermally Stimulated Depolarization Bands

1976

J. Electrochem. Soc.

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It is shown by theoretical argument and by experiment that only in the case of a first order kinetics polarization do the TSD peaks occur invariably at a fixed temperature. Otherwise their position is shifting in a characteristic way with changing initial polarization. In the case of a space charge release, for example, the maximum temperature is increasing with polarization temperature and polarization time. Thus, l~eak position data for varying polarization conditions allow one to decide in particular whether a peak is due to a first order depolarization process, e,g., complex rearientation, or to the release of a space charge 9The thermalIy stimulated depolarization (TSD) of polar crystals by an increasing temperature usually shows several bands or peaks. This indicates that the depolarization is realized by several different processes. Two such processes are well known: the relaxation of aligned impurity-point defect complexes (1) and the relaxation of a space charge caused by mobile point defects accumulated at the electrodes (2. 3). But there are stiI1 other processes which cause TSD peaks which have not yet been identified (1, 4).It is one of the fundamental problems of any investigation of TSD to relate the observed peaks to specific depolarization processes. From the experimental point of view, there are three quantities which characterize a given TSD peak, on which an analysis may be based: the maximum position, the magnitude of the peak, and the slope of the initial rise of the peak. The magnitude of the peak is eventually (1) a measure of the number of defects causing the polarization. The determination of the slope of the initial rise, which should yield the activation energy af the depolarization process, is in general a delicate task and if the peaks overlap too much, possibly no meaningful value can be obtained at all. However, it is comparatively easy to determine the approximate peak positions. We shall show how the peak position depends on the initial polarization of a sample, and that this can provide some information on the depolarization processes causing the peaks in question. Some General Considerations Concerning TSDThe TSD is usually investigated by measuring the "depolarization current" Im(t,T) ofa polarized sample of cross section A and thickness L which is connected to a gaIvanometer. The measured current density im(t,T) = Im(t,T)/A is equal to the sum of the charge transport rate density e. j(x,t) and the displacement current density OD (x,t)/Ot at any arbitrary cross section of the investigated sample. Under ideal conditions, the measurement is carried out without any potential drop between the electrodes, AV = E(x,t) 9 dx = 0, and without any charge transfer to the electrodes, i.e., j(o,t) = j(L,t) = 0. Under these conditions solely the displacement current densitydue to the redistribution of charges inside the sample is measured. In general, there exist several different causes of polarization. However, we shall restrict ourselves here Key words: thermally stimulated depolarizatio...