Putting the squeeze on ferroelectrics
DOI: 10.1063/1.4796793
Piezoelectric materials display cause and effect between mechanical deformation and electric field; applying either generates the other. Ferroelectric materials have a spontaneous, measurable electric dipole moment even in the absence of an electric field; an applied field can greatly increase that polarization. Combining the two properties is the technological basis of many actuators and other devices. The most useful such devices have their largest electromechanical response in a narrow region of their compositional phase diagram, a region dubbed the morphotropic phase boundary (MPB). To meet the appropriate criteria, modern devices are generally made from complex, engineered materials. Enter some physicists from the Carnegie Institution of Washington, who found an MPB in a pure compound—lead titanate—under pressure. The researchers obtained both synchrotron x-ray diffraction and Raman spectroscopy data for PbTiO3 under low-temperature, high-pressure conditions and discovered that even a pure material can show very large piezoelectric effects—in fact, the largest yet known. The scientists suggest that mechanical pressure could be replaced with chemical pressure by substituting a smaller atom with similar polarizability for Pb. Designing simple electromechanical materials using chemical substitution could greatly decrease costs and increase utility of ultrasonic and other actuators. (
