Tape casting of piezo ceramic polymer composites

1-3 Piezoelectric composites are used as ultrasonic transducers for naval s onar devices, medical diagnostic systems, and non-destructive materials tes ting. Their excellent coupling behaviour to ultrasonic signals in wafer is due to the high fraction of polymer as the matrix and a very fine structure d piezoelectric ceramic, which allows an effective transfer of the hydrosta tic waves from the polymer to the ceramic. The aim is to obtain a composite of maximum hydrostatic performance characterised by d(h) x g(h) (d(h): hyd rostatic charge coefficient; g(h): hydrostatic voltage coefficient), which allows a detection of signals even with low intensity. Different processing routes are known to manufacture such 1-3 composites, but there is a need f or a flexible, low cost process for medium quantities. Tape casting is a ve ry adaptable method to produce such composites. Strips were cut into PZT gr een tapes line by fine. Subsequently, the sheets were sintered and stacked, by using spacers between the sheets. The free spaces are filled with polym er, and finally the edges of the composite are cut off to remove the frame of the PZT-sheets. Different techniques were investigated to structure the green tapes without damaging them and to preserve the fine structure of the tapes during firing by avoiding warpage. (C) 1999 Elsevier Science Limited . All rights reserved.