Ferroelectric studies in stretched and corona charged SAN films

Ferroelectric properties in the stretched and corona poled films of poly(styrene-co-acrylonitrile) were investigated. The D-E hysteresis loops were studied in the stretched SAN films (S=2.5X) corona poled at poling field E_p≈45 MV/m and poling temperature T_p =85°C in the temperature range 28 to 115°C. The remanent polarization and coercive field were found to decrease with temperature. A phase transition from ferroelectric to paraelectric is believed to be taking place in the film in the vicinity of its glass transition temperature T_g≈112°C. The dielectric relaxation of the order of 13 has been obtained in these films. The application of Frohlich theory to the thermally stimulated current results for the SAN films poled under identical conditions provides the value of orientational correlation factor g≈1.6 which corroborates the cooperative motion of dipoles in these films and explains its ferroelectric behaviour