Local characterization of piezoelectric and electrostrictive thin films subjected to high electric fields

Local piezoelectric measurements, performed on PZT thin films and on electrostrictive PMN-PT plates, subjected to very high d.c. electric fields, are presented. The thin films were obtained by pulsed laser deposition from commercial PZT targets. The PMN-PT thin plates where obtained by sintering, via the columbite process. A special device, that allows the local measurement of the piezoelectric constant while the same area of the sample is subjected to the bias field, was constructed. An electrical circuit allows the separation of the two signals in order to have only the low intensity ac. Signal from the film detected by the instrument. The sample can be scanned over its surface and local measurements of the piezoelectric constant can be performed with a spatial resolution of about 1 mm and a sensitivity of less than one tens of pC/N. The d.c electric field can be varied between 0 and few kV/mm. Results concerning spatial variation of the piezoelectric constant of piezoelectric thin films and the induced piezoelectric constant of electrostrictive materials under high intensity bias electric fields are presented and discussed.