Some piezoelectric materials may be 'fakes'

Piezoresponse force microscopy (PFM) is the most widespread technique for characterising piezoelectric properties at the nanoscale, i.e., for determining the ability of some materials to generate electricity when subjected to mechanical stress and deforming in response to a voltage. Piezoelectricity is used in a wide variety of applications, including pregnancy ultrasounds, injection motors, sensors that measure deformations, actuators and sonar, among others. Piezoresponse force microscopy not only determines whether a material is piezoelectric, but also its degree of piezoelectricity, and it is particularly important for applications of these materials in microelectronics and nanotechnology.

from Nanotechnology News - Nanoscience, Nanotechnolgy, Nanotech News http://bit.ly/2Z2kdJq