Prikshit Gautam

EFFECT OF PROCESSING CONDITIONS ON ELECTRICAL PROPERTIES OF CaCu3Ti4O12 CERAMICS

CaCu3Ti4O12 (CCTO) ceramics were prepared by the solid-state reaction route. Effect of sintering time was studied on the polarization (P) versus electric field (E) behavior. Unlike conventional ferroelectric hysteresis loop, PE hysteresis behavior in CCTO ceramics was observed to exhibit ferroelectric-like loop where polarization does not saturate but gives a maximum value. Remnant polarization and maximum polarization was observed to increase with sintering time. Current (I)–voltage (V) characteristics shows a nonlinear behavior making them useful for varistor applications. Coefficient of non-linearity (α) is also found to depend on sintering duration.

Fabrication and Characterization of Bismuth Lanthanum Titanate (Bi3.25La0.75Ti3O12) Thin Films for FeRAM Devices

Thin films of Lanthanum doped Bismuth Titanate (Bi3.25La0.75Ti3O12) (BLT) have been prepared and characterized for their applications in ferroelectric random access memory (FeRAM) devices. The films have been characterized via X-ray diffraction (XRD), atomic force microscopy (AFM), capacitance-voltage (C-V), ferroelectric (P-E) and current-voltage (J-V) characteristics. The effect of thickness on these characteristics has also been investigated. Thickness variation shows significant effect on the morphology and ferroelectric properties of the films. The nature of the J-V characteristics was observed to be independent of the thickness of the films. Three distinct regions, i.e., ohmic, trap filled limited and Childs law were explicitly observed in J-V characteristics. The J-V behavior of BLT thin films was found to follow the Lamperts theory of space charge limited conduction in an insulator with traps.

Structural and Electrical Properties of Lead Zirconate Titanate 0–3 Composite Films

Modified sol-gel method alongwith the infilteration process have been used to deposit dense, crack-free ferroelectric lead zirconate titanate (PZT) 0–3 ceramic/ceramic composite films of composition Pb(Zr0.52Ti0.48)O3 and thickness greater than 10 μm onto a platinum coated silicon substrate. PZT powder with the same composition was dispersed using a dispersant ESL400 in PZT sol to obtain a slurry. The slurry and the sol were alternatively deposited on the substrate followed by drying, pyrolysis and final annealing at 750°C to get single phase perovskite structure of the film. Thickness of the film was determined by SEM. Surface morphology of the film was studied by AFM. Raman spectrum of the film depicts coexistence of rhombohedral and tetragonal phases. Temperature dependence of dielectric constant shows that the films exhibit diffused phase transition rather than relaxor behavior. The remanant polarization (Pr) and coercive field (Ec) of the resulting film are 13.5 μC/cm2 and 57 kV/cm respectively.

Dielectric Functions of Niobium Doped Bi3.25La0.75Ti3O12 Thin Films Using Spectroscopic Ellipsometry

Ferroelectric thin films of Nb doped Bi3.25La0.75Ti3O12 (BLT) were prepared by chemical solution deposition method onto Pt/Ti/SiO2/Si(100) substrates using spin coating technique. From the X-ray diffraction analysis it was found that films were polycrystalline with single phase. The optical properties of the Nb doped BLT thin films were investigated at room temperature in the 0.72–6.2 eV energy range using spectroscopic ellipsometry (SE). Double Tauc–Lorentz (DTL) dispersion relation was successfully fitted in the uv/visible region. Value of the full width at half maxima (Г) in dielectric function plots increased with Nb doping. This increase in FWHM may be attributed to the increase in the trap density in forbidden band which consequently decreases the value of Eg. The optical band gap energy (E g d) was found to decrease with increase in Nb doping concentration. This decrease in E g d with doping may be due to the changes in the defect concentration present in the structure.

Dielectric and Ferroelectric Studies on Sol-Gel Derived Calcium Modified Lead Zirconate Titanate Ceramics

Bulk samples of Pb(1-x)CaxZr0.52Ti0.48O3 (x = 0,0.02,0.04,0.06,0.08,0.1) have been synthesized by sol-gel process using lead acetate trihydrate, calcium acetate hydrate, zirconium propoxide and titanium propoxide as the starting materials. The dependence of ferroelectric phase transition temperature Tc as a function of calcium substitution has been investigated. A linear decrease of Tc is observed with increasing calcium concentration. The variation of room temperature dielectric constant and that of maximum value of dielectric constant corresponding to the phase transition temperature are explained by the microstructural studies. XRD patterns of the samples show that all the compositions sintered at 1200°C are having single phase with perovskite structure. P-E hysteresis loop measurements showed that calcium modified PZT ceramics have higher Pr values than that of pure PZT composition prepared by sol-gel method. The composition with 4 mol% calcium has the highest value of Pr, 25.2 μC/cm2 and lowest Ec, 9.6 kV/cm.