Influence of nitrodopamine-functionalized barium titanate content on the piezoelectric response of poly(vinylidene fluoride) based polymer-ceramic composites

Piezocomposites were elaborated by incorporating barium titanate (BT) ceramic particles into a poly(vinylidene fluoride) (PVDF) matrix. A key issue of the process is to obtain the electroactive β crystal phase in PVDF by stretching the polymer-ceramic composite. For this purpose, as well as in view of enabling the poling step of the composite film, the interfacial cohesion between ceramic and polymer has to be efficient and this has been achieved by nitrodopamine functionalization of the ceramic surface (nBT). The structural evolution associated to the deformation-induced α-β crystal phase transformation in the presence of nBT has been analyzed in situ under stretching. The piezoelectric properties of these composites have been characterized in parallel poling. In the range of nBT filler loading under investigation, it is shown that the d33 piezoelectric coefficient of the composite is modulated by the ceramic content. Polymer matrix dominated response yields a negative d33 value at low nBT content. Interestingly enough, the piezoelectric response is null at 26 wt% nBT loading and the piezoelectric coefficient becomes positive beyond that filler fraction.