THE WAFER FLEXURE TECHNIQUE FOR THE DETERMINATION OF THE TRANSVERSE PIEZOELECTRIC COEFFICIENT (D(31)) OF PZT THIN-FILMS

This paper describes a simple and inexpensive method for evaluating th e transverse piezoelectric coefficient (d(31)) of piezoelectric thin f ilms. The technique is based upon the flexure of a coated substrate wh ich imparts an ac two-dimensional stress to the piezoelectric film. Th e surface charge generated via the mechanical loading is converted to a voltage by an active integrator. Plate theory and elastic stress ana lyses are used to calculate the principal stresses applied to the film . The d(31) coefficient can then be determined from knowledge of the e lectric charge produced and the calculated mechanical stress. For 52/4 8 sol-gel lead zirconate titanate (PZT) thin films, the d(31) coeffici ent 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.