Impedance , Electrical Conductivity and Piezoelectric Studies on Nb 5 + doped ( Bi 0 . 5 Na 0 . 5 ) 0 . 94 Ba 0 . 06 TiO 3 - PVDF 0 - 3 composites

The present work makes use of experimental ac complex impedance data to obtain the electrical parameters like electrical conductivity and activation energy of ((Bi0.5Na0.5)0.94Ba0.06TiO3+0.2 wt%Nb2O5)– PVDF 0-3 composites with 10, 20 and 30 vol. percentage of ((Bi0.5Na0.5)0.94Ba0.06TiO3+0.2 wt%Nb2O5) in the frequency range 1kHz–1 MHz over a temperature range of 35C-145°C. SEM micrographs exhibited good dispersion of almost spherical dense grains (sizes ranging between 8-14 μm). Cole-Cole analysis for frequencydependent complex impedance data indicated the presence of grain-boundary effect along with the bulk contribution, thereby showing the NTCR character for the composites, especially in the lower frequency and higher temperature regime. Results were also analyzed via the electric modulus formalism. Experimental results evidenced that the recorded relaxation phenomena include contributions from both the polymeric matrix and the presence of the reinforcing phase. Temperature dependent ac conductivity data also endorsed the NTCR character for the composites. Activation energy data allowed an insight into the mechanism of hopping of charge carriers in the materials. Ceramic filler concentration dependent increase of d33 (ranging between 20-40 pC/N) of the composite was seen to follow the first order exponential growth type of equation.