M. Priya

Electrical conductivity measurements on gel grown KDP crystals added with urea and thiourea

Pure and impurity added (with urea and thiourea) KDP single crystals were grown by the gel method using silica gels. Electrical conductivity measurements were carried out along both the unique axis and perpendicular directions at various temperatures ranging from 30 to 140‡ C by the conventional two-probe method. The present study shows that the conductivity in KDP crystals, for both the impurities considered, increases with the increase in impurity concentration and temperature. Activation energies were also determined and reported.

A study of structural, optical and dielectric properties of Eu2O3 doped borate glass

Recent technological applications have generated more interest in the studies of different types of glasses. The wide applications of glasses take place due to their interesting properties such as low thermal expansion, high softening temperature, high resistance to chemical attack, high refractive index with low dispersion and mechanical strength. Eu2O3 doped borate glasses were successfully synthesized by melt quenching method. The X-ray diffraction (XRD) spectra revealed that these glasses had amorphous nature. Optical properties of prepared samples were characterized by photoluminescence studies. The dielectric properties of glass samples were studied for different frequencies and different temperatures.

Enhancement in the optical and magnetic properties of ZnO:Co implanted by Gd3+ nanoparticles

Rare-earth metal Gadolinium (Gd3+) co-doped with ZnO:Cobalt (Co) nanoparticles are fabricated by simple, quick and versatile chemical precipitation technique. Structural, optical and magnetic studies have been carried out for Gd co-doped ZnO:Co nanoparticles. The structural analysis shows that Gd co-doped samples are single phase of wurtzite structure, where the average crystallite size of the samples is found to be nanometric regime. The morphology and chemical composition of the nanoparticles were studied using scanning electron microscopy and energy dispersive spectroscopy. Scanning electron microscopic study shows increase in particle size. In photoluminescence spectra, Gd co-doped samples show a remarkably prominent blue shift in UV region with that of pure ZnO with an increase in the intensity of green emission. The broad green emission due to the oxygen vacancy related to defect centers is present below the conduction band introduced by the Gd impurities in ZnO nanoparticles. When compared to the Co doped ZnO, Gd with ZnO:Co exhibits a clear ferromagnetism at room temperature with high coercivity. The unprecedented ferromagnetic property is attributed to the effective Ruderman–Kittel–Kasuya–Yosida exchanging interaction and change with dopant concentration Gd3+ into ZnO:Co nanoparticles. These results strongly suggest the future development of efficient luminescence and magnetic materials at normal room temperatures with Gd and Co doped ZnO nanostructures for spintronic devices.

Influence of Samarium Oxide ions on structural and optical properties of borate glasses

We have successfully synthesized Samarium oxide (Sm2O3) doped borate glasses by conventional rapid melt quench method. The prepared batch was melted at suitable transition temperature and to improve the crystalline phases, glass was kept at 500°C for 7 h. The X-ray diffraction (XRD) pattern identified the amorphous nature of glass and photoluminescence emission properties proved the optical properties of Sm2O3 doped borate glass. Fourier transform infrared spectroscopy (FTIR) and FTRaman studies suggested that Sm2O3 could modify the properties of glass

Studies on electrical properties of MgO/Pr6O11 nanocomposite

Magnesium Oxide/Praseodymium Oxide (MgO/Pr6O11) nanocomposite was prepared by sol–gel method. X-ray diffraction analysis confirmed the cubic structure. The morphology was studied using high-resolution scanning electron microscopy picture. The AC/DC conductivity and dielectric properties were investigated in the frequency range of 1–4 KHz and in the temperature range of 303–573 K. The results showed that the dielectric constant and the tangent loss were frequency and temperature dependent. The AC/DC conductivity at different temperatures indicated that the conductivity was thermally activated. The activation energy for AC/DC conductivity was calculated using Arrhenius plot.

Effect of solvent and annealed temperature on band gap energies of MgO nanoparticles

Novel two-dimensional nanostructures of magnesium oxide nanoparticles were synthesized by simple reflux method by changing the solvent and annealing temperature. The structural and surface morphology were investigated using X-ray diffraction spectra and High-resolution scanning electron microscopy (HR-SEM). The XRD spectrum showed that the synthesized MgO samples are pure cubic MgO. The HR-SEM picture showed that the MgO nanoparticle prepared with ethanol as a solvent gives different morphologies such as nanoflakes, nanoflowers and nanosheet at low temperature. At high temperature, the flake shape changes into spherical shape. The micro strain is calculated using Williamson-Hall plot method. The optical properties of synthesized MgO nanoparticle studied by using UV-Visible and Photoluminescence (PL) spectra. UV emission and a broad visible emission band in photoluminescence (PL) spectra further demonstrates that the potential applications of the material in optoelectronics. The particle size, morphology and band gap of the synthesized MgO nanoparticle is highly influenced by the solvent and annealing temperature.

Synthesis and characterization of NiFe2O4, CoFe2O4 and CuFe2O4 thin films for anode material in Li-ion batteries:

The searches for advanced battery materials are endless. Ferrites have drawn much attention as a potential anode material in Li-ion battery. Nanocrystalline transition metal ferrite MFe2O4 (M = Ni, Co and Cu) thin films were deposited by spray pyrolysis technique over antimony doped tin oxide substrate. The phase and surface morphology were studied by X-ray diffraction and scanning electron microscope measurements, respectively. Magnetic property, film thickness and electrochemical performance of the materials are studied. The result shows that the films are of single phase, with cubic spinel structure for NiFe2O4 and CoFe2O4 and tetragonal structure for CuFe2O4. Magnetization studies reveal that the films are ferrimagnetic in nature. Electrochemical measurement reveals NiFe2O4 and CuFe2O4 are having good recyclable nature, which can be used as potential anode material for Li-ion batteries.

Synthesis and Study of Optical properties of MgO based TM oxide (TM=Cu, Mn and Zn) nanocomposites

A nanocomposite of MgO based transition metal (TM) oxide (TM=Zn, Mn, and Cu) was synthesized using sol-gel method. The powder x-ray diffraction confirmed the phase purity and particle size. The surface morphology and elemental composition were examined by High resolution scanning electron microscopy and energy-dispersive x-ray spectroscopy. The change in optical band gap of the synthesized nanocomposites, by increasing the Mg content was determined using UV–vis spectra and the luminescent properties were analyzed using photoluminescence spectra.

Optical and magnetic properties of Yb ion-doped cobalt-based ZnO nanoparticles for DMS applications

Well-crystalline structured ZnO nanoparticles with cobalt (Co) and ytterbium (Yb) multiple ions doping were successfully synthesized by the chemical precipitation technique. The structures, optical and magnetic properties of the samples were analysed with X-ray diffraction (XRD), UV–visible spectroscopy and magnetic measurements, respectively. In the XRD pattern of the pure ZnO and Yb co-doped samples, the formation of highly crystalline phase of pure ZnO was observed even at high Yb concentration. UV–vis spectra show a strong UV absorbance for all the samples with different absorbance maxima. Magnetic characterizations have shown that the sample with 1% Yb co-doped ZnO : Co nanoparticles exhibited a clear ferromagnetic (FM) behaviour at room temperature. The X-ray photoelectron spectral peaks for Yb 4f ions reveal Yb occupation of both Yb3+ as well as Yb2+ states. Hence, it can be confirmed that a clear FM behaviour at room temperature was exhibited by an imbalanced valence state of Yb that strongly interacted with the Co2+. When compared to the Co-doped ZnO, Yb co-doped ZnO exhibits a clear ferromagnetism at room temperature with high coercivity due to the contribution of both 3d and 4f exchange interaction with the host matrix.