Optimization of 1-3 relaxor-PT single crystal polymer composite

PZN-PT single crystals exhibit an ultra-large longitudinal bar mode coupling coefficient. (k(33)) of similar to 0.94. The thickness mode coupling coefficient (k(t)), however, is just comparable to soft PZT ceramics. in order to utilize the advantages of single crystals, it is desirable to incorporate them into a 1-3 composite structure. The single crystals possess a very large effective radial mode-coupling coefficient (k(p)) and are elastically soft compared with PZT ceramics. As a result, 1-3 single crystal polymer composites exhibit a very large k(p) of similar to 0.7 and only moderately enhanced k(t) (similar to 0.8) when typical epoxies are used as the matrix material. A filled epoxy with microspheres was characterized and successfully filled in the kerfs of a PZT-5A piezocomposite. 1-3 PZT-5A/polymer composite test samples demonstrate avery high k(t) of similar to 0.69 and a low k(p) of similar to 0.20 as compared to 0.65 and 0.26 for k(t) and k(p) without microsphere loading. In addition, the frequency constant of the radial mode was reduced by 24%. As a second method of improving performance, a high compliance polymer was incorporated into the design The coupling coefficient k(t) of the composite increased from 0.80 to 0.83 as a result of this soft filler. The high Poisson's ratio of the soft filler was the limitation to achieving high coupling. The quasi-static model developed by Hashimoto and Yamaguchi was used to predict the complete electromechanical constants of a 1-3 composite. The agreement between experiment and model was within 5% for the thickness made, while for the k(31) mode, the theoretical data was 20% higher than the experimental data.