Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Method for measuring the properties under high electric field properties

We developed a method for measuring dielectric and piezoelectric properties of thick films under large fields (comparable to coercive field). For measurements of the dielectric polarization, the system consists of a charge amplifier, a lock-in analyser, an oscilloscope and function generator with voltage amplifier.

The voltage signal is applied on a sample and the resulting charge (proportional to polarization) is first amplified by the charge amplifier and then analysed by the lock in amplifier and displayed on the oscilloscope.

The lock-in amplifier signal gives us possibility to analyse nonlinear properties by analysing different harmonics (usually the first free) while the oscilloscope gives the polarization response-driving signal hysteresis.

For piezoelectric measurements, we use an ultra-low displacement laser interferometer. Measured strain signal is again analysed by the lock-in amplifier and displayed on the oscilloscope. The oscilloscope signal gives total strain-electric field hysteresis, whereas lock-in amplifier signal gives information on different harmonics.

By comparing the results of the dielectric and piezoelectric measurements, done under identical driving field conditions, it is possible to draw conclusions on the different mechanisms responsible for the dielectric and piezoelectric nonlinearity and hysteresis. Besides scientific importance, these results are useful as a feed back to materials preparation and device designing tasks.

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Reported by

Ecole Polytechnique Fédérale de Lausanne
EPFL STI-IMX - Ecublens
1015 Lausanne
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