Enhancement in pyroelectric detection sensitivity for flexible LiNbO₃/PVDF nanocomposite films by inclusion content control

The pyroelectric properties of polymer-ceramic nanocomposites of Lithium niobate/Poly (vinylidene fluoride) or LiNbO₃/PVDF (abbreviated LN/PVDF) for thermal/infrared sensing applications are reported in this work. The composites are prepared by dispersing nanoparticles of LiNbO_3, with particle size in the range 45–65 nm, in β-PVDF matrix at varying volume fractions, and cast in the form of flexible films by solvent-cast technique. The electro-active β-phase of PVDF is confirmed by powder X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC) analyses. The thermal properties, thermal conductivity and specific heat capacity, of the composites are determined by a photothermal technique. The prepared films have been poled in a high dc electric field, and their pyroelectric and dielectric properties measured by direct methods. From these data the pyroelectric figures of merit of the composite films have been determined and their values compared with corresponding values for pure PVDF film. The Shore hardness of the films has been measured to estimate the extent to which the flexibility of the films is affected by the addition of ceramic. Significant enhancement in pyroelectric sensitivity has been obtained with increase in volume fraction of LiNbO₃ nanoparticles. However, this enhancement is at the expense of the flexibility of the composite; so one has to strike a balance between the two while selecting a suitable composition for the development of pyroelectric sensors with these materials. The results of this work provide guidelines for this selection.