Displaying items by tag: SpetAne_eng

MXene consists of metallic layers, that can easily slide with respect to each other like sheets in reams. A phase transition has been revealed measuring the elastic modulus of films. It should be a new type of ferroelectricity found in bilayers of other 2D materials, where a polarization is generated between the layers sliding with respect to each other. The sliding ferroelectricity is studied with sophisticated techniques at the nanoscale and promises exceptional improvements in ferroelectric memories and Nanoelectronics, but we simply measured the Young’s modulus of a thick film.

“Elastic precursor effects during the Ba_1-xSr_xTiO₃ ferroelastic phase transitions”, published in Physical Review Research, is the result of a collaboration between ISM-CNR, Cambridge Earth Sciences (Cambridge University - England), Federal University of São Carlos (UFSCar - Brazil) and Xi’an Jiaotong University (China).  
The elastic softening in the paraelastic/paraelectric phases of Ba_1-xSr_xTiO₃ extends to the highest measured temperature (850 K) for Ba-rich compounds and can be fitted with a power law (T-Tc)^k where k ranges between 1.5 in SrTiO₃ and 0.2 in BaTiO₃. An alternative Vogel-Fulcher type analysis is also considered. The amplitude of the precursor softening increases continuously from SrTiO₃ to BaTiO₃ and is still 33% of the unsoftened Young’s modulus at 750 K in BaTiO₃. This proves that the high temperature elastic properties of these materials are drastically affected by precursor softening.

The project aims at studying and improving some classes of organic and metal-organic piezoelectric materials (in which a stress causes an electric field and vice versa), which recently come into the limelight due to their unexpectedly high electromechanical coupling constants.