Space Charge Measurement by Electroacoustic Method: Impact of Acoustic Properties of Materials on The Response for Different Geometries

Abstract

The pulsed electro-acoustic method (PEA) allows dynamic measurements of space charge density distribution with good temporal resolution and is suitable for both flat samples (a few hundred micrometers thickness) and coaxial cable samples. The response obtained by the technique is tributary to the electro-mechanical properties of the materials through which acoustic waves propagate. Hence, when dealing with multilayer dielectrics, the acoustic properties of individual layers are to be taken into account. Also, the acoustic attenuation and dispersion phenomena, especially when dealing with relatively thick samples, affect the space charge resolution at positions far away from the sensor. Therefore, application of a calibration procedure on experimental signals is necessary to recover space charge density profile from PEA raw signals and to provide real results on charge density both on its temporal and spatial dependence. We illustrate here in different samples configurations, spanning from flat samples, multi-layer and cable geometry, how the calibration is achieved and how the acoustic properties of materials impart the response.

Macro-dipoles in soft/hard expanded-polytetrafluoroethylene + fluoroethylenepropylene (ePTFE + FEP) fluoropolymer-film systems for high-output piezoelectric ferroelectret-transducer applications

“…As shown in figure 2(b), the charge densities of the bottom macro-dipole appear to be higher than those of the upper macro-dipole. This observation may essentially be an artifact caused by stronger attenuation of the acoustic waves during propagation to the PVDF sensor at the bottom from the charges near the top electrode [37].…”