Preparation and Characterization of the Ferroelectric Potassium Nitrate: Poly(vinyl alcohol) Composite Films

Abstract

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.

Evaluation of Structural and Ferroelectric Properties in Spray Deposited (NH<SUB>4</SUB>)<SUB>0.39</SUB>K<SUB>0.61</SUB>NO<SUB>3</SUB>: Poly(vinyl alcohol) Composite Films

“…It has been reported that thin films deposited on the different metal substrates shows excellent ferroelectric, electrical, and dielectric properties. 12 17 18 20 The composite films were annealed in vacuum at their deposition temperatures for 24 h and then slowly cooled to room temperature. Indium electrodes with different cross-sectional areas were deposited by thermal evaporation under the vacuum 2 0 × 10 −5 mbar onto the upper surface of the sample.…”

“…The crystallite size was determined using Scherrer relation. 12 It was found to increase with the deposition temperature. The crystallite size seems to play an important role in the stabilization of ferroelectric phase III in the composite films at room temperature.…”

“…12 17 19 27 28 Therefore, the new developed peaks in spray deposited NKN:PVA composite films could originate due to ferroelectric phase III. The presence of ferroelectric phase III at 2 = 29 80 ± 0 05 in the PVA matrix at room temperature in these composite films would imply that these composite films are expected to exhibit ferroelectric properties.…”

“…[9][10][11] Usually, the ceramic-polymer composites have been prepared by the addition of ceramic material into polymer matrix by solvent cast, sol-gel, melt press, intercalation techniques, ultrasonic spray setup. [12][13][14][15][16] These soft ceramics have low coercive field of order kV/cm, and to use them in the devices operating at relatively low voltage needs fabrication in the film form. Furthermore, the proper combination of the ceramic and polymer allows the fabrication of the new materials with desired ferroelectric properties such as high remanent polarization and low coercive field.…”

“…These films also possess good electromechanical properties, flexibility, and reasonable mechanical strength. 12 17 18 Recently, the dielectric, thermal, ferroelectric phase stability, switching and structural properties of spray deposited pure NKN and NaNO 2 films and composite films of KNO 3 , NaNO 2 and CsNO 3 with PVA have been studied ARTICLE by our group. 12 17-21 It has been reported earlier that spray deposited (NH 4 0 39 K 0 61 NO 3 films showed clear ferroelectric properties and switching properties at room temperature.…”