Tape casting of piezo ceramic/polymer composites

摘要

1-3 Piezoelectric composites are used as ultrasonic transducers for vaval sonar devices, medical diagnostic systems, and non-destructive materials testing. Their excellent coupling behaviour to ultrasonic signals in water is due to the high fraction of polymer as the matrix and a very fine structured piezoelectric ceramic, which allows an effective transfer of the hydrostatic 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: hydrostatic 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 for a flexible, low cost process for medium quantities. Tape casting is a very adaptable method to produce such composites. Strips were cut into PZT green tapes line by line. Subsequently, the sheets were sintered and stacked, by using spacers between the sheets. The free spaces are filled with polymer, 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.