Characterizing unpoled piezoelectric ceramic film by Lamb-waves

Determination of the physical properties of unpoled ceramic films on metallic substrates is considered; the problem is important because these properties may be quite different than those in the bulk, which are caused by the effects of porosity. It is shown that the density and elastic constant C/sub 33/ can be determined by a modification of the previously used modal frequency spacing (MFS) method, involving cut-off frequencies for longitudinal and shear sagittal plane modes. This method has the advantage of great simplicity compared with the standard inversion approach. Numerical calculations show that good accuracy of the order of 2% can be obtained for density and for C/sub 33/ for simulations of PZT films on stainless steel, platinum, and aluminum plates.