Scientists at \u00c9cole Polytechnique F\u00e9d\u00e9rale de Lausanne (EPFL) in Switzerland have made an important discovery about the structure of barium titanate, a material used in everyday objects. Their findings refute existing theories on the displacement of the material\u2019s atoms.<\/p>\n
Barium titanate is a ferroelectric material used in nearly all electronic devices\u2014computers, smartphones and even electric cars. It\u2019s used to make the sensors and capacitors they run on, for example. \u201cA single smartphone generally has around 700 capacitors containing barium titanate, and trillions of these capacitors are made every year,\u201d says Dragan Damjanovic, an EPFL professor and head of the Group for Ferroelectrics and Functional Oxides at EPFL\u2019s School of Engineering. Despite barium titanate\u2019s widespread use, however, researchers still don\u2019t fully understand how it works. \u201cThere are of course theoretical models out there, but some of their key predictions have never been experimentally confirmed. So that\u2019s what we set out to do,\u201d says Damjanovic.<\/p>\n
Emad Oveisi, a senior scientist at EPFL\u2019s Interdisciplinary Center for Electron Microscopy, suggested that Damjanovic use his center\u2019s Titan Themis\u2014one of the world\u2019s most powerful electron microscopes\u2014for his research. The Titan Themis enabled the scientists to observe the atomic structures of barium titanate and barium-strontium titanate in the cubic phase. That was back in 2015, when they obtained the first images; it took another five years to analyze and verify their results. \u201cUntil now, researchers believed that the atoms move in several directions in a very short timeframe. But our experiments showed that they tend to prefer certain directions, meaning there are nanometric-sized areas where all the atoms move in the same way. That completely changes how we view these materials and their atomic structure,\u201d says Oveisi.<\/p>\n
Thanks to the advanced image analysis methods, the scientists were able to identify where in the material the atoms move in an orderly fashion. \u201cWhen we talk about movements, we\u2019re actually referring to displacements that take place on a picometer scale\u2014that is, one order of magnitude smaller than the atoms themselves,\u201d says Oveisi. Damjanovic adds: \u201cEven though the displacements are extremely small, they have repercussions on a much larger scale. For instance, if we expose the nanometric areas we identified to a high-frequency electric field like those in smartphones, the areas heat up.\u201d His team\u2019s findings could therefore be extremely useful in better understanding energy loss in these kinds of materials.<\/p>\n
\u201cThe next step will be to develop materials where the size of the displacement area is minimized in order to enhance the material\u2019s properties,\u201d says Damjanovic.<\/p>\n