Ferroelectric Phase Stability Studies in Spray Deposited KNO₃:PVA Composite Films

Abstract

The composite films of potassium nitrate (KNO 3 ):poly(vinyl alcohol) (PVA) have been prepared at different temperatures by spray-deposition technique. Ferroelectric hysteresis loops were traced at room temperature for the composite films using modified Sawyer and Tower circuit. The X-ray diffraction studies confirm the existence of ferroelectric phase III of KNO 3 in the composite films at the room temperature, where this phase in pure KNO 3 films is known to exist in the temperature range 1101-1241C. The composite films deposited at 2001C shows the optimum remanent polarization, P r B17 lC/cm 2 . The P r was studied in the frequency range 10 Hz-1 kHz. The stability of the P r in the composite films exhibits improved fatigue compared with that of quenched KNO 3 films. The capacitance-voltage (C-V) characteristics exhibits butterfly features which supports the presence of ferroelectric phase in the composite films. The atomic force microscopy images show that the composite films have uniform dispersion of KNO 3 particles in the PVA matrix.

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

“…The image of the composite film containing 50 wt.% of Kno 3 show the uniform distribution of Kno 3 in PVa matrix and grain size of ~225 nm. Earlier studies using atomic force microscopy (aFM) technique also revealed grain size of similar order in these films having this composition [52]. However, the clustering of the Kno 3 particles has been observed in the composite films above 50 wt.% composition of Kno 3 .…”

Switching Kinetics in Cesium Nitrate: Poly (Vinyl Alcohol) Composite Film

“…In this region t < t s, the finite grain size effect on the switching current is negligible since the size of domain is much less than the grain size. Therefore, the theoretical fit to switching current in the region t ≥ t s was obtained using equation (2), which takes into account the effect of grain size. Hence the switching time t s is the time at which the switching kinetics changes from independent of grain size to grain size limitations.…”

“…The polarization reversal takes place by applying an external electric field greater than its coercive field and this property can be utilized for the memory devices application [1,2]. Thus, the study of switching transients in the composite films can be useful in understanding the switching mechanism as well as to find its potential applications in memory devices.…”

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 is well known that 180 domain switching is easier than the 90 domain switching. 17 34 35 Moreover, the orientation of 90 is directly related to the back switching phenomenon. The least percentage of back switching suggests that the interaction between the domains and structural defects is significantly reduced in the composite films which could be responsible for larger P r and smaller coercive field, E c in composite films.…”

“…The back switching percentage was calculated from the hysteresis loop characteristics. 17 34 35 Back switching (%age) was calculated in the composite films of NKN:PVA (1:1) deposited at 130, 150, 170, 200 and 250 C and found to be 20. 26, 19.56, 14.78, 21.29 and 23.23% respectively.…”