New Treatment can Artificially Create Physical Properties in Materials

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Researchers from the Technical University of Freiberg and the University of Siegen in Germany collaborated to conduct a study which demonstrates that the physical properties of strontium titanate (SrTiO3) in its single crystal form can be modified using a simple electrical treatment. The mineral strontium titanate is studied for its superconducting properties.

The treatment has been recently explained in the journal Applied Physics Letters, from AIP Publishing, and generates the piezoelectric effect known as piezoelectricity - where mechanical stress leads to electricity - in a material that did not originally experience piezoelectric effects.

This could be of great importance as today’s technologically-oriented society constantly makes ever-increasing demands for unusual properties and new materials.

Atoms and electrons that arrange themselves in periodic patterns produce crystalline materials. A crystal’s atomic structure is much like a piece of a cross-stitching pattern, only at a ten million times smaller scale. Although a cross-stitching technique might be confusing at first, it can be easily repeated to fill the available space once it is known.

Nature builds crystals in much the same way; it “learns” to connect atoms in a unit cell, and then repeats the pattern to fill the available space to make a crystal lattice.

Looking at a crystal structure is similar to looking at a fabric using a magnifying glass. Researchers can apply external stimuli (e.g. an electric voltage or stretch) to a crystal using the technique of X-ray diffraction, to see how various connections or atomic "stitches" respond.

The idea for this work was born when I was giving a colloquium talk in TU Freiberg, presenting our new technique for time-resolved X-ray diffraction and investigating piezoelectric material. Our colleagues in Freiberg had been investigating artificially created near-surface volumes of SrTiO3 crystals, with properties different from the normal bulk SrTiO3.

Semën Gorfman, Physicist, University of Siegen

Researchers from the University of Siegen used X-ray diffraction that is mobile to develop unique experimental equipment to explore crystal structures under a periodically differing field and could connect to any instrument, such as a synchrotron beamline or a home-lab X-ray diffractometer.

Since the measurements are non-routine, this experimental equipment makes our research truly unique and original. It turned out that the technique developed at Siegen, was ideally matched to the research direction that the Freiberg team was working on, so we came up with the hypothesis to be tested (piezoelectricity in field-modified near surface phase of SrTiO3 crystal), and a suggested experimental method (stroboscopic time-resolved X-ray diffraction), performed the experiment and got results.

Semën Gorfman, Physicist, University of Siegen

This study demonstrates that new physical properties can be developed through artificial means, describing the piezoelectric effect in the artificially created new phase of strontium titanate, a material that does not see piezoelectric effects under normal conditions.

We believe that physical properties of migration field induced polar phase in SrTiO3 opens a new and interesting chapter for research. The challenge now is to make the effect practical so that it can be used for devices.

Semën Gorfman, Physicist, University of Siegen

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