The wafer flexure technique for the determination of the transverse piezoelectric coefficient (d31) of PZT thin films

This paper describes a simple and inexpensive method for evaluating the transverse piezoelectric coefficient (d(31)) of piezoelectric thin films. The technique is based upon the flexure of a coated substrate which imparts an ac two-dimensional stress to the piezoelectric film. The surface charge generated via the mechanical loading is converted to a voltage by an active integrator. Plate theory and elastic stress analyses are used to calculate the principal stresses applied to the film. The d(31) coefficient can then be determined from knowledge of the electric charge produced and the calculated mechanical stress. For 52/48 sol-gel lead zirconate titanate (PZT) thin films, the d(31) coefficient was found to range from -5 to -59 pC/N and is dependent on poling field. (C) 1998 Elsevier Science S.A. All rights reserved.