Dissipation factors spectroscopy

Material response is typically studied using either direct (constant) applied voltage (DC) or alternating applied voltage (AC). The AC response as a function of frequency is characteristic of a material. In the future, such electric spectra may be used as a product identification tool, much like IR spectroscopy. Factors such as current strength, duration of measurement, specimen shape, temperature, and applied pressure affect the electric responses of materials. The response may be delayed because of a number of factors including the interaction between polymer chains, the presence within the chain of specific molecular groupings, and effects related to interactions in the specific atoms themselves. A number of properties, such as relaxation time, power loss, dissipation factor, and power factor are measures of this lag. The movement of dipoles (related to the dipole polarization (P) within a polymer can be divided into two types an orientation polarization (P ) and a dislocation or induced polarization. 

Samples for dielectric spectroscopy were prepared by sputtering 100 nm of Au in an Ar plasma onto both sides of the freely standing films. Disks 9.5 mm in diameter were punched out of the metallized films. These disks were used to measure both the dielectric permittivity with an HP 4192 Impedance Analyzer and the dissipation factor with a GenRad 1615-A Capacitance Bridge. 

The change in D can be obtained by measuring the impedance spectroscopy [9] or by fitting the oscillation decay [14], In the former method, a broader resonance peak is indicative of a larger dissipation factor. In the latter case, the measurement of D is based on the fact that the amplitude of oscillation (A) or the output voltage over the crystal decays as an exponentially damped sinusoid when the driving power of the piezoelectric oscillator is switched off at t = 0 (Fig. 1.2) [16] ... 

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