The energy distribution of localized states in polystyrene, based on isothermal discharge measurements

Watson, P.K.

doi:10.1088/0022-3727/23/12/002

Cited by 85 publications

(27 citation statements)

References 11 publications

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“…The current is proportional to the number of carriers excited from Em. Meanwhile, through the plotting of I(t)t against t, the change of the charges detrapping from the traps at time t can be estimated [27].…”

Section: Effect On Surface Chargementioning

confidence: 99%

Effects of surface fluorination on dielectric properties and surface charge behavior of water absorbed polyimide film

Guo

2015

IEEE Trans. Dielect. Electr. Insul.

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With the advantages of excellent physical, chemical and thermal properties, polyimide (PI) film has been widely used as insulation material in electrical and mechanical equipment. However, PI presents water absorption capacity because of the existence of carbonyl and amine groups in the molecular chain. When exposed in moisture conditions, PI film will be degraded. Therefore, the dielectric breakdown occurs and irremediable damage will appear in insulation system. The dielectric properties of PI film are largely influenced by the absorbed water and humidity. Direct fluorination is an effective method of surface modification which can improve the properties of original material from many respects, such as the wettability, barrier properties and chemical stability. In this paper, to study effects of fluorination on dielectric properties of moistened PI films, the PI specimens were surface fluorinated for 15, 30, 45 and 60 min respectively. The specimens without fluorination were also prepared for the contrast. Then the specimens were immersed in high purity water for 6, 12 and 24 hours. The water absorption, permittivity and breakdown strength under different fluorination and immersion time were measured. Meanwhile, given that the existence of surface charge had a critical influence on the breakdown characteristics, the corona charging tests were conducted at room temperature and the charge dissipation was investigated. Obtained results show that fluorination can reduce the water intake capacity and enhance the breakdown strength of PI in moisture conditions. The decay process of surface charge and the change of detrapping charges in PI films are affected by both the fluorination and the immersion time.

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Section: Effect On Surface Chargementioning

confidence: 99%

Effects of surface fluorination on dielectric properties and surface charge behavior of water absorbed polyimide film

Guo

2015

IEEE Trans. Dielect. Electr. Insul.

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“…Detrapping kinetics may become the main factor determining ISPD in the case that transit time of charge carriers is lower than their mean detrapping time especially when the electric field is high. Then we can explain the ISPD in the view of energy [28]. Although some literature interpreted ISPD in the perspective of energy, the classification of the traps and the distinction between electron/hole carriers still need further research.…”

Section: Introductionmentioning

confidence: 95%

The energy distribution of trapped charges in polymers based on isothermal surface potential decay model

Zhou

Min

et al. 2015

IEEE Trans. Dielect. Electr. Insul.

161

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Space charge formation in polymeric materials can cause some serious concern in real operation, because it has significant influence on the performance of polymers. For example, space charge in some insulating materials can severely distort the electric field, even lead to materials degradation. On the contrary, in the case of its applications, space charge stored in electrets can greatly improve their properties. It is therefore important to understand trapped charge distribution in materials as it is considered to be a novel indicator for effective evaluation of aging status and electric withstanding strength of insulating materials. In this paper, a model based on isothermal surface potential decay (ISPD) is proposed to study the distribution of trapped charges by considering the physical mechanism of the detrapping process. By measuring the ISPD characteristics of polymeric materials and fitting the data according to the assumption of shallow and deep traps, the distribution of trapped charges is obtained, which may be related to the change of aggregation structure of polymers. In order to verify the model, it is used to analyze different ISPD decay curves of polypropylene (PP) and low density polyethylene (LDPE), as well as the ISPD data of PP electrets with/without pressure expanding treatment. The results show that the proposed ISPD model is effective and convenient. Two peaks are observed on the curve of the trapped charge density versus the trap level. The obtained distribution of the trapped charges in polymers can reveal the different nature of electron/hole traps and the different transportation behavior of hole/electron carriers, i.e., the electron-type traps show an inter-chain character while the character of hole-type traps is intra-chain. In addition, the distribution of trapped charge is further related to aggregation structure of PP and LDPE, as well as PP electrets with/without pressure expanding treatment.Index Terms -Space charge, isothermal surface potential decay (ISPD), trapped charge density, aggregation structure.

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“…According to Eq. (19) and (20), this leads to ϕ PF ≈ 172 for T = 300 K and then to κ ≈ 0.12. The last value is smaller than the expected one, but the corresponding plot is in rough agreement with data for t > t T (Fig.…”

Section: Discussion Of An Experimental Examplementioning

confidence: 87%

“…These models are more or less refined, considering for instance the absence of trapping [8][9][10][11][12][13], partial trapping [4], deep trapping [15,17], or the presence of space-charge in the sample [10,18]. Original interpretations have also been given thanks to so-called demarcation energy models [19,20] or in terms of surface detrapping [5].…”

Section: Introductionmentioning

confidence: 99%

Potential decay experiments for the characterization of electron transport. Modelling and discussion

Mady

Renoud

Ganachaud

et al. 2005

Physica Status Solidi (b)

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Potential decay experiments are considered as an efficient method for studying transport in insulators. Interpretation of their results is nevertheless still delicate, mainly because of the difficulty in controlling the quantity of deposited carriers (dose). This work is concerned with an apparatus which allows an accurate control of the dose. An adequate modelling of potential decay, based on analytical and numerical calculations, is then proposed for time-dependent, field-dependent and trap-limited mobilities. It is shown that representing the data with a convenient set of dimensionless variables greatly facilitates their interpretation, indicating for instance directly either the mobility depends on the field or not. Expressions of the experimental observable and characteristic features associated with the various transport models are derived. Finally, an example of data analysis is discussed in detail to illustrate how our conclusions can be used in practise to extract information about transport of excess electrons in insulators.

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The energy distribution of localized states in polystyrene, based on isothermal discharge measurements

Cited by 85 publications

References 11 publications

Effects of surface fluorination on dielectric properties and surface charge behavior of water absorbed polyimide film

Effects of surface fluorination on dielectric properties and surface charge behavior of water absorbed polyimide film

The energy distribution of trapped charges in polymers based on isothermal surface potential decay model

Potential decay experiments for the characterization of electron transport. Modelling and discussion

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