Aging of pzt/polymer 1-3 composites

In the present study, previously tested PZT7A/Araldite D 1-3 piezoelectric composites with ceramic volume fractions ranging from 0.2 to 0.8 are re-examined to reveal the effect of aging. The samples have been stored under ambient conditions for more than five years and are now tested again using the original IEEE method. The changes in the electromechanical coupling factors and other material parameters are negligibly small, showing that the material does not suffer greatly from aging degradation. Besides using the standard IEEE procedure, the composites are also tested by the method of Sherrit et al which uses more exact values for the parallel and series resonance frequencies and takes into account the mechanical and dielectric loss of the ceramic-polymer composites. It is found that the major discrepancy in the results obtained from the two methods is due to the choice of different frequency values. The inclusion of loss leads to a negligible effect on the electromechanical coupling factors of the composites and a 10% increase in the thickness mode coupling factor of PVDF.