Abstract
Thick film piezoelectric ceramic sensors have been successfully depositedon different metallic substrates with different shapes by a sol–gel spraytechnique. The ball-milled bismuth titanate fine powders were dispersed intoPZT solution to achieve the gel. The films with desired thickness up to200 µm have been obtained through the multilayer coating approach. These thickfilms were also effectively coated onto thin sheet metals of thickness down to25 µm. Self-support films with flat and shell geometries were made. Piezoelectricity was achievedusing the corona discharge poling method. The area of the top silver paste electrode wasalso optimized. The center frequencies of ultrasonic signals generated by these filmsranged from 3.6 to 30 MHz and their bandwidth was broad as well. The ultrasonicsignals generated and received by these ultrasonic transducers (UTs) operatedin the pulse/echo mode had a signal to noise ratio more than 30 dB. The mainadvantages of such sensors are that they (1) do not need couplant, (2) can serve aspiezoelectric and UT, (3) can be coated onto curved surfaces and (4) can operate up to440 °C. The capability of these thick film UTs for non-destructive evaluation of materials at440 °C has been demonstrated.
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