Preparation and characterization of the ferroelectric potassium nitrate: poly(vinyl alcohol) composite films

The composite films of ferroelectric potassium nitrate (KNO3):poly(vinyl alcohol) (PVA) with different weight percentages of KNO3 have been prepared at 200 degrees C using the spray-deposition technique. The remanent polarization (Pr) and peak current density for all composite films was estimated by tracing the polarization-electric field (P-E) hysteresis loop and current density-electric field (J-E) loop, respectively, using a modified Sawyer-Tower circuit. Pure KNO3 is known not to exhibit any ferroelectricity under ambient conditions, but the X-ray diffraction (XRD) studies of PVA:KNO3 composite films reveal the presence of a ferroelectric phase III of KNO3 in the composite films at room temperature. The composite film containing KNO(3):PVA in equal proportions shows maximum Pr and peak intensity ratio of approximately 20.10 microC/cm2 and 2.67, respectively, at room temperature. The J-E and capacitance voltage (C-V) characteristics exhibit butterfly features that supports the presence of a ferroelectric phase in the composite films. The field emission scanning electron microscopy (FE-SEM) image of the composite film containing equal proportions of KNO3 and PVA shows the homogenous distribution of spherical grains of KNO3 of size approximately 225 nm.