by Dr. Long-Qing Chen, Professor of Materials Science and Engineering and Professor of Engineering Science and Mechanics, Penn State. Piezoelectric crystals can generate electrical charge under an applied mechanical force and change shape under an applied electrical field. They have many applications in electromechanical devices such as ultrasonic transducers for medical imaging, actuators, etc. The piezoelectricity of a crystal is measured by the amount of strain that a crystal exhibits under an applied electric field or the amount of charge that a crystal generates under a stress. It has been a long-standing challenge to simultaneously achieve high piezoelectricity and light transparency in a crystal since the highest performance piezoelectric crystals are ferroelectrics containing high-density light-scattering domain walls within their domain structures. This presentation will discuss our recent computation-guided, rather surprising, discovery of simultaneous near-perfect light transparency and ultrahigh piezoelectricity in Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystals by understanding the ferroelectric domain evolution mechanisms under alternative current (AC) electric field poling using phase-field simulations. The newly discovered transparent ferroelectric crystals are expected to open up a range of electro-optical-mechanically coupled devices from high-throughput photoacoustic imaging to transparent actuators for haptic applications.
by Dr. Susan Trolier-McKinstry, Professor of Materials Science and Engineering and Electrical Engineering, Penn State February 17, 2020 Piezoelectric materials couple electrical and mechanical energies, and as such, offer an interesting platform to study numerous functional properties. Piezoelectric thin films are ubiquitous in filters and duplexers for cell phones and are of increasing interest in low voltage microelectromechanical systems (MEMS) for sensing, actuation, and energy harvesting. This talk will discuss how materials are optimized for these applications, as well as examples of the use of piezoelectric films over a wide range of length scales. The key figures of merit for resonators, actuators, and energy harvesting will be discussed, with emphasis on how to achieve these on practical substrates. Recent work on doped AlN for cell phone resonators will be reviewed. In addition, the roles of crystallographic orientation and domain state will be described for low voltage actuators and mechanical harvesters in thin films with the perovskite structure. Examples of integration into MEMS structures will also be discussed, including adaptive optics for X-ray telescopes, low frequency and non-resonant piezoelectric energy harvesting devices, inkjet printers, and ultrasound transducers for miniaturized medical diagnostics.
by Dr. Jon-Paul Maria, Penn State, 1/27/2020. This presentation summarizes the research activities in the Maria group that involve thin film synthesis. The major categories include high mobility conducting oxides for IR plasmonic applications, reactive nanoaminates for chemical energy storage and propulsion, entropy stabilized oxides, high entropy transition metal carbines, and thin film explorations to find new functional materials. In all cases, research in the group endeavors to advance the science and understanding of synthesis in parallel to property engineering.