Jasbir S. Hundal

Analysis of ferroelectric polarization switching in (NH4)0.39K0.61NO3 films using nucleation limited switching model

The polarization switching transients of spray deposited ferroelectric (NH4)0.39K0.61NO3 (NKN) films has been analyzed with nucleation limited switching (NLS) model by considering domain growth limited process. The experimentally measured microscopic polarization switching curves fitted well with NLS model and the characteristic switching times obeyed the Lorentzian distribution function. The local field variation was found to be minimum at pulse amplitude 15 V, which makes the polarization reversal more probable. The value of spontaneous polarization, Ps and coercive field, Ec was found to be 6.58 μC/cm2 and 4.10 kV/cm, respectively. The value of Ps from the switching and P-E loop is in good agreement with each other. The field emission scanning electron microscopy and atomic force microscopy images of the NKN film reveal the formation of nanoparticles of NKN.The polarization switching transients of spray deposited ferroelectric (NH4)0.39K0.61NO3 (NKN) films has been analyzed with nucleation limited switching (NLS) model by considering domain growth limited process. The experimentally measured microscopic polarization switching curves fitted well with NLS model and the characteristic switching times obeyed the Lorentzian distribution function. The local field variation was found to be minimum at pulse amplitude 15 V, which makes the polarization reversal more probable. The value of spontaneous polarization, Ps and coercive field, Ec was found to be 6.58 μC/cm2 and 4.10 kV/cm, respectively. The value of Ps from the switching and P-E loop is in good agreement with each other. The field emission scanning electron microscopy and atomic force microscopy images of the NKN film reveal the formation of nanoparticles of NKN.

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 200degC 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 KNO3:PVA in equal proportions shows maximum Pr and peak intensity ratio of approximately 20.10 muC/ 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 ~225 nm.

Ferroelectric and Magnetic Properties of Hot-Pressed BiFeO3-PVDF Composite Films

The ferroelectric and magnetic properties of hot-pressed BiFeO3- (BFO) polyvinylidene fluoride (PVDF) composite films have been studied. The BiFeO3 (BFO) ceramics have been synthesized by a rapid liquid phase sintering technique. The X-ray diffraction (XRD) studies revealed that the impure phase observed in pure BFO ceramics was significantly reduced in the composite films. The presence of both ferroelectric and magnetic hysteresis loops confirms the multiferroic nature of the composite films at room temperature. A well-saturated ferroelectric hysteresis loop with a remanent polarization (𝑃𝑟)∼4.8 μC-cm−2 and coercive field (𝐸𝑐)∼1.55 kV/cm has been observed in composite thin films at room temperature. The magnetic hysteresis loops were traced at room temperature with SQUID. The remanent magnetization (𝑀𝑟)∼3.0×10−3 emu/gm and coercive field (𝐻𝑐)∼0.99 kOe was observed in the composite film. The magnetic polarization of the composite films has found to be enhanced as compared to pure BFO and correlated to reduction in BFO impure peak intensity.

Correlation of piezoelectric effect and TSC in stretched polystyrene-acrylonitrile films

The piezoelectric coefficient d/sub 31/ of stretched SAN (polystyrene-co-acrylonitrile) films has been measured under different poling and stretching conditions. The maximum average value of d/sub 31/ has been found to be 3.85 pC/N for 2.5/spl times/ stretched films, corona poled at field E/sub P//spl sime/50 MV/m, and poling temperature T/sub P/=85/spl deg/C. The TSC (thermally stimulated current) experiments were performed to obtain the contribution of the polarization to the piezoelectric activity. The shrinkage effect and the TSC results are correlated to elucidate the molecular relaxation processes. The elastic modulus, crystallinity and polarization parameters are correlated to the piezoelectricity. The contributions of the dimensional and the local field effects to the piezoelectric activity in SAN are discussed.

Ferroelectric and Switching Properties of Spray Deposited NaNO2: PVA Composite Films on Porous Silicon

The ferroelectric and switching properties of spray deposited sodium nitrite (NaNO2) - poly vinyl alcohol (PVA) composite films on porous silicon template have been analyzed. The image of field emission scanning electron microscope (FE-SEM) shows that the average pore size varies from 800 to 1250 nm with the anodization time of silicon. The remanent polarization of the composite films is dependent on the pore size of the silicon. The optimum value of remanent polarization (Pr) = 41μC/cm2 is observed in NaNO2: PVA composite film for pore size 1250 nm. The switching kinetics of the composite films has been analyzed by different theoretical model. The switching current data are fitted well with infinite-grain model (IGM) in the lower time region and deviate in later time region. The nucleation limited switching (NLS) model gives excellent agreement with the experimental polarization reversal transients throughout the whole time range.

Bias Dependent Current-Voltage (I–V) Characteristics of Ferroelectric Potassium Nitrate: Poly (Vinyl Fluoride) Composite Films

The current-voltage (I–V) characteristics of the ferroelectric potassium nitrate (KNO3): poly vinyl fluoride (PVF) has been investigated. The current–voltage characteristics gave the peak-to-valley ratio (PVR) of 4.5:1 for the forward bias voltage of +2V at room temperature. The non-linear and butterfly features of the capacitance-voltage (C–V) curves strongly corroborate the presence of ferroelectricity in the composite films. The Negative Differential Resistance (NDR) phenomenon has been observed with applied dc bias voltages and indicates the Resonant Tunneling type characteristics.

Investigation on structural and ferroelectric properties of spray deposited Cs 1-x K x NO 3 : PVA : composite films

The ferroelectric and fatigue properties of spray deposited K - substituted cesium nitrate: poly (vinyl alcohol) composite films have been studied. The XRD pattern confirms the presence of ferroelectric phase of CsNO3 in the composite films upto doping concentration of 7.5%. The elemental analysis has been studied using EDX measurements. It is observed the remanent polarization (Pr) increases linearly that with doping concentration and optimum value of Pr = 9.2 μC/cm2 was found. The fatigue measurements also show improvement in K - substituted composite films. The switching time has been found to reduce four times in the K - substituted films. The C - V characteristics of the composite films show the butterfly feature and also confirm presence of ferroelectricity in the composite films.

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

The effect of pulse amplitude on the switching properties of cesium nitrate: poly (vinyl alcohol) composite film at room temperature has been studied. The switching response of the composite film was studied using the bipolar square pulses. The switching current transients were analyzed using finite grain model (FGM) and infinite grain media (IGM). The Matlab programming based upon the assumptions of FGM and IGM theories is used to fit the experimental data with the theoretical. The microscopic parameters such as effective dimensionality, switching time, nucleation rate, and domain wall velocity have been estimated. The polarization current and domain wall velocity exhibited exponential dependence on the pulse amplitude.

Polarization Switching Behavior of Ferroelectric (NH4)0.39K0.61NO3 Films

The polarization switching transients of spray-deposited ferroelectric (NH4)0.39K0.61NO3 (NKN) films have been investigated. Modified Sawyer-Tower circuit has been used to trace the hysteresis loop (P-E). The value of maximum polarization, Ps and coercive field, Ec was found to be 6.58 µC/cm2 and 4.10 kV/cm respectively. The polarization fatigue study has been carried out. The experimental polarization switching transients were fitted well with the Kolmogorov-Avrami-Ishibashi (KAI) nucleation theory The maximum polarization switching current (imax) and maximum switching time (tmax) have been measured as a function of the applied field. The activation field (), dimensionality (n) and switching time have been determined by employing the KAI model to the experimental switching transients. The atomic force microscopy (AFM) has been employed to estimate the grain size (~ 72 nm) and root mean square roughness (rms) (~ 130nm) of the (NH4)0.39K0.61NO3 films and has been correlated with the switching properties.