  For pyroelectric detector application materials should have low dielectric
constant, high pyroelectric coefficient, large non volatile polarization at
small applied electric field and low specific heat. Large field (greater than
1200kV/cm) is need to pole ferroelectric polymer poly (vinylidene fluoride)
(PVDF) and it has low sensitivity compared to other pyroelectric materials. To
increase non volatile polarization at low poling field and to increase
pyroelectric coefficient, LiTaO3 (LT) nano particles were added to PVDF matrix
to make LT/PVDF composite. It is important to study the dielectric properties
of the composite (to be used in detector application) because dielectric
constant varies with volume fraction of filler and with frequency. Nano
composite films of LT/PVDF with different volume fraction (i. e fLT = 0.047,
0.09 and 0.17) of LT were prepared by dispersing LT nano particles in solution
of PVDF. The dielectric properties of LT/PVDF composite were studied by varying
the volume fraction of LT. The dielectric permittivity of LT/ PVDF composites
increased compared to PVDF as the volume fraction of LT increases but the loss
tangent is almost constant at higher frequency. In low frequency region, for
fLT = 0.17 the dielectric permittivity of composite is greater than PVDF and
LT. The dielectric loss tangent is also increased from 0.04 to 0.175 as fLT
increases from 0 to 0.17 at 1 kHz. The dielectric permittivity behavior of
composite has been explained using percolation model and space charge
polarization model.
