Electrical and optical properties of pure and silver nitrate-doped polyvinyl alcohol films

Although biaxially-oriented polypropylene thin film is a common dielectric for many high voltage pulsed power capacitor applications, the electrical conductivity under high field at elevated temperature is mostly unknown. Such knowledge is valuable not only for better understanding of the origin and transport mechanisms of the charge species at high field, but also for gaining insight for improving breakdown strength and electro-thermal modeling of high energy density, pulsed power capacitors. In this work, the conduction mechanism was investigated and the conductivities near breakdown were inferred through the use of a thermal runaway criterion and the measured breakdown strength at various temperatures. Results suggested that conduction is by hopping with a thermal activation energy that is about 0.76 eV and is field-independent. Such finding allows the use of an Arrhenius term and a field-dependent term to describe the field-dependent conductivity up to breakdown.

High field conduction in biaxially oriented polypropylene at elevated temperature

Polyvinyl alcohol (PVA) and mercury sulfide (HgS) polymer nanocomposite were prepared using the solution casting and the in situ chemical reduction of mercury nitrate (Hg(NO3)2) and sodium sulfide (Na2S) in aqueous solutions of PVA as capping for different molar content of Hg(NO3)2 and Na2S. The nanocomposites films were characterized by Fourier transform infrared, X-ray diffraction (XRD), and scanning electron microscopy. The XRD results for the nanoparticles revealed the hexagonal structure of the HgS, (α-phase). The influence of embedded HgS nanoparticles on the conductivity and dielectric properties of PVA films are investigated, over the frequency range 1 kHz–1 MHz, and the temperature range 30–110 °C. The variation of ac-conductivity with a frequency of the films follows Jonscher’s universal power law and found to be increased with increasing temperature, frequency and nanoparticle content. The variation of frequency exponent (s) indicated that the conduction mechanism was correlated barrier hopping model. The dielectric constant (ɛ′), and dielectric loss (ɛ″) was found to decrease with increasing frequency, but increase with increasing temperature and HgS nanoparticles content. The dc-conductivity (σ
 dc
 ) increase with increase of HgS concentration, and follows Arrhenius behavior in the investigated temperature region.

Electrical conductivity and dielectric characteristics of in situ prepared PVA/HgS nanocomposite films

Growth, structure, dielectric and AC conduction properties of solution grown PVA films

The structural and optical properties of thin lead oxide films were studied. Thin films were prepared by reactive dc magnetron sputtering of lead (Pb) targets in an Ar/O2 mixture. The structure has been determined by x-ray diffraction measurements, which show that crystalline lead oxide films of different composition (PbO, PbO1.44, Pb2O3, and PbO2) have been formed upon increasing oxygen flow (partial pressure). This result is confirmed by Raman spectroscopy. The effect of postdeposition annealing on the structural properties of PbO films reveals that the film structure is governed by both energetics and kinetics. X-ray reflectivity measurements were used to determine the thickness, density, and roughness of the films. The calculated film density values are almost equal to the bulk density of the material, showing that compact, nearly void free films are formed. The optical properties of the films have been studied from the reflectance and transmittance spectra recorded by optical spectroscopy measurement...

Structural and optical properties of thin lead oxide films produced by reactive direct current magnetron sputtering

The electrical conductivity (σ) of polyvinyl acetate (PVAc) films as a function of the iodine (I2) concentration, temperature (T), and voltage (U) is studied and an increase of about four orders of magnitude in σ is observed due to the doping of I2 in PVAc at room temperature For pure PVAc, σ increases exponentially with T, whereas in the case of PVAc: I2 films, σ first increases with T, reaches a maximum and then decreases and the maxima in σ vs T curves, shift towards lower temperatures with the increase in I2 concentration It appears from the I—U—T characteristics of pure and iodine doped PVAc films that the Poole-Frenkel effect is the dominant charge transfer mechanism On doping I2 in PVAc, an optical absorption band peaking at ≈ 370 nm, is observed and is attributed to charge transfer complexes



Die elektrische Leitfahigkeit (σ) von Polyvinylazetatschichten (PVAc) wird als Funktion der Jodkonzentration (I2) Temperatur (T) und Spannung (U) untersucht und ein Anstieg von etwa vier Grosenordnungen in σ wird infolge der Joddotierung in PVAc bei Zimmertemperatur beobachtet Fur reines PVAc nimmt σ exponentiell mit T zu, wahrend im Fall der PVAc:I2-Schichten σ zuerst mit T zunimmt, ein Maximum erreicht und dann wieder abnimmt, das Maximum in der σ uber T-Kurve verschiebt sich dabei zu niedrigeren Temperaturen, wenn die I2-Konzentration zunimmt Aus den I—U—T-Charakteristiken von reinen und Jod-dotierten PVAc-Schichten folgt, das der Poole-Frenkel-Effekt der dominante Ladungstransfermechanismus ist Infolge der Dotierung von I2 in PVAc wird eine optische Absorptionsbande bei ≈ 370 nm beobachtet und Ladungstransferkomplexen zugeschrieben

Electrical conduction in pure and iodine-doped polyvinyl acetate thick films

The thermal sensitization process for the enhancement of photoconductivity in tetragonal lead monoxide has been investigated. At a critical annealing temperature the photosensitivity has been found to have a maximum value (≅5×102) while the conductivity is observed to have a minimum value (≅10−10Ω cm). The transient response of the photocurrent exhibits an overshoot, the height of which is strongly dependent on the annealing temperature. These and other findings have been explained on the basis of sensitization due to the creation of two types of centres in the material.

Sensitization of photoconductivity in tetragonal lead monoxide

The electrical conduction in Ag-polypropylene-Ag sandwich samples is studied measuring the dependence of current (I) on voltage (U) and temperature (T). The experimental results of I–U–T relationships show that Schottky field assisted thermionic emission is the dominant conduction mechanism in the temperature range 390 to 440 K. The metalinsulator work function is calculated to ≈ 1.83 eV. Hysteresis and polarization effects are also observed in the I–U characteristics in this range of temperature. Contribution due to bulk polarization is suggested in the conduction mechanism besides the Schottky emission.

Electrical conduction in polypropylene thin films

Photopolarization process in orthorhombic lead monoxide

The charging and discharging characteristics of corona charged polyvinyl acetate films are investigated as a function of thickness. The saturation potential at constant corona field is found to vary with film thickness in a parabolic manner. The rise and decay transients of the surface charge are found to follow closely the theoretical expressions derived on the basis of space charge formation in the bulk of the polymer during corona charging.



Die Aufladungs- und Entladungscharakteristiken von Polyvinylazetatschichten, die in einer Koronaentladung aufgeladen werden, werden als Funktion der Filmdicke untersucht. Das Sattigungspotential bei konstantem Koronafeld variiert parabolisch mit der Filmdicke. Das An- und Ab- klingen der Oberflachenladung befolgt sehr gut die theoretischen Ausdrucke fur den Aufbau von Raumladungen im Volumen des Polymers wahrend der Koronaaufladung.

P. C. Mehendru

Papers

Electrical conduction in pure and iodine-doped polyvinyl acetate thick films

Sensitization of photoconductivity in tetragonal lead monoxide

Electrical conduction in polypropylene thin films

Photopolarization process in orthorhombic lead monoxide

Surface charge decay characteristics in polyvinyl acetate films