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New Delhi, India

Raghuvanshi S.,The Interdisciplinary Center | Kapoor M.,University of Delhi | Tyagi S.,Gargi College | Kapoor S.,The Interdisciplinary Center | And 3 more authors.
Molecular Breeding | Year: 2010

Rice is one of the pillars of world-wide food security. Improvement in its yield is necessary to mitigate hunger of millions of people who depend on rice as a staple. Decoding rice genome sequence is expected to complement efforts being made to improve rice and its yield. The information about more than 32,000 genes, regulatory elements, repeat DNA, and DNA markers opens-up new horizons for molecular analysis and genetic enhancement not only for rice but also for other cereal crops. In the post-genomic era, significant progress has been made on defining transcriptome and epigenome as well as gene discovery by way of forward and reverse genetic approaches. Efforts are on to fill the gap between the genome and the phenotype. This may lead to regular practice of genomics-assisted breeding of rice. © 2009 Springer Science+Business Media B.V. Source


Sachdeva A.,University of Delhi | Kumar M.,National Physical Laboratory India | Luthra V.,University of Delhi | Luthra V.,Gargi College | Tandon R.P.,University of Delhi
Applied Physics A: Materials Science and Processing | Year: 2011

We report here the formation of single phase lead zirconate titanate (PZT) nanopowder with composition Pb(Zr0.52Ti0.48)O3 and average crystallite size 12-20 nm, synthesized by sol-gel process. The phase evolution of PZT gel powder, heat treated at temperatures 550, 650 and 800°C was monitored by X-ray diffraction (XRD) and X-ray photo-electron spectroscopy (XPS). The high resolution XPS spectra of Pb4f, Zr3d, Ti2p and O1s show that PZT with pure perovskite structure is obtained at 800°C while at lower temperatures pyrochlore phase co-exists with perovskite phase. The XRD results also support this analysis. We have also identified the pyrochlore phase using XPS by analyzing the corresponding variations in the FWHM values, peak positions and the separation between the spin doublets of Pb, Zr and Ti associated with it. The composition of the final powder obtained with pure perovskite structure is calculated and is close to the designed value. © 2011 Springer-Verlag. Source


Arora M.,National Physical Laboratory India | Sachdeva A.,University of Delhi | Luthra V.,Gargi College | Tandon R.P.,University of Delhi | Pant R.P.,National Physical Laboratory India
Integrated Ferroelectrics | Year: 2010

Nanocrystalline PLZT thin films of composition Pb1-xLa xZr0.52Ti0.48 (x = 0, 2, 5%) were deposited on silicon substrates by sol-gel process using lead acetate trihydrate, lanthanum nitrate hydrate, zirconium propoxide and titanium propoxide as lead, lanthanum, zirconium and titanium precursor materials. Experimental studies have been made on solitary waves in 2 mol% lanthanum doped sol-gel derived lead zirconate titanate thin films. The solitary waves are generated under the influence of external alternating electric field, which has the same frequency as the external field. These solitary waves propagate through the thin film upto its boundary and then reflect back. The magnitude of the solitary waves attenuates as they move away from the electrodes and their phase reverses on reflection. For certain frequencies of the external electric field, solitary waves exhibit resonance effect. Distortion in hysteresis loops has been demonstrated on the basis of solitary waves propagation in the film having different electrode area. Copyright © 2010 Taylor & Francis Group, LLC. Source


Sachdeva A.,University of Delhi | Luthra V.,University of Delhi | Luthra V.,Gargi College | Gautam P.,University of Delhi | Tandon R.P.,University of Delhi
Integrated Ferroelectrics | Year: 2010

Bulk samples of Pb(1-x)CaxZr0.52Ti 0.48O3 (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. Copyright © 2010 Taylor & Francis Group, LLC. Source


Sachdeva A.,University of Delhi | Gautam P.,University of Delhi | Luthra V.,University of Delhi | Luthra V.,Gargi College | Tandon R.P.,University of Delhi
Integrated Ferroelectrics | Year: 2010

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(Zr0.52Ti 0.48)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/cm 2 and 57 kV/cm respectively. Copyright © 2010 Taylor & Francis Group, LLC. Source

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