Study of the charge profile of thermally poled electrets

TL;DR

This study compares LIPP and PEA methods to analyze charge profiles in thermally poled electrets, revealing insights into polarization mechanisms and the effectiveness of each technique.

Contribution

It introduces a comparative analysis of LIPP and PEA methods for studying charge profiles in thermally poled electrets, highlighting their respective capabilities.

Findings

LIPP shows simpler charge profiles, while PEA detects more polarization mechanisms.

Charge profiles become antisymmetric at higher temperatures.

Injection of negative carriers influences charge trapping near electrodes.

Abstract

The charge profile of thermally poled electrets has been studied using two different methods, laser induced pressure pulse (LIPP) and pulsed electroacoustic (PEA), to gain insight into the mechanisms that are activated and assess which is the most appropriate method to study the charge profile. Disc--shaped PET samples have been conventionally poled to activate both the alpha and the rho relaxation and, right after, partially discharged up to a temperature Tpd. In this way, samples with a different combination of dipolar and space charge polarization have been obtained. Both LIPP and PEA reveal asymmetric profiles for Tpd below the glass transition temperature, that progressively become antisymmetric for higher temperatures. The shape and evolution of the charge profiles can be explained assuming injection of negative carriers from the anode that enhances the trapping of positive carriers near this electrode. It can be observed that PEA is able to detect a wider variety of polarization mechanisms in the system while LIPP gives a simpler picture of the charge profile.