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Highly exciting interferometry

PTB interferometer for precise length measurements has been specially upgraded to measure the length change in functional materials.

PTB-News 2.2015
Especially interesting for

manufacturers of functional materials

the automotive industry

aeronautical engineering


The piezoelectrically induced length change in functional materials has been measured at PTB for the first time at high temperatures and with lateral resolution. For this purpose, a new sample environment was created which can be integrated into the existing interferometer for precise length measurements.

Height topography of the PZT sample (diameter: 15 mm, thickness: 2 mm) at 20 °C and 100 °C, with and without applied voltage.

Functional materials such as, e.g., piezoceramics, are used in numerous application fields, among other things in the automotive industry, in aeronautical engineering, in metrology, in energy production and in process monitoring. Use at high temperatures is increasingly aimed at. Developing such new materials, together with the corresponding metrological infrastructure, is the aim of the European cooperation project METCO. Concretely, the activities revolve around the ability to measure the coupling between mechanical, electrical and thermal properties in a wide temperature range. PTB's task hereby consists in measuring changes in length interferometrically, at high temperatures (currently up to 200 °C) and with an electric field applied (from -2 kV/mm to +2 kV/mm). To this end, a special sample environment was developed at PTB and tested with a commercially available lead zirconate titanate (PZT) ceramic at various temperatures.

From the measured piezoelectrically induced length change, the piezoelectric coefficient was determined at 20 °C as well as at 100 °C. The results are in agreement with measurements which were carried out by partners with commercially available measuring systems; they could also be reproduced on other samples under investigation. The advantage of PTB's interferometer resides in the fact that it is an imaging system, so that not only point-by-point length measurements, but also spatially resolved length variations (length topography) of the entire surface of the sample are possi-ble. This provides additional information, e.g., on inhomogeneities or edge effects.

After initial tests have been successfully completed, the next step will consist of investigating high-temperature piezo-materials which have been newly developed by our project partner, the University of Leeds (UK).


Guido Bartl
Department 5.4 Interferometry on Material Measures
Phone: +49 (0)531 592-5411
E-mail: guido.bartl(at)ptb.de


Scientific publication:

T. Stevenson, T. Quast, G. Bartl, T. Schmitz-Kempen, P. Weaver: Surface mapping of field-induced piezoelectric strain at elevated temperature employ-ing full-field interferometry. IEEE Trans Ultrason Ferroelectr Freq Control 62, 88–96 (2015)