Ch. Rama Krishna

Synthesis and structural characterization of Co2+ ions doped ZnO nanopowders by solid state reaction through sonication

Cobalt ions doped zinc oxide nanopowder was prepared at room temperature by a novel and simple one step solid-state reaction method through sonication in the presence of a suitable surfactant Sodium Lauryl Sulphate (SLS). The prepared powder was characterized by various spectroscopic techniques. Powder XRD data revealed that the crystal structure belongs to hexagonal and its average crystallite size was evaluated. From optical absorption data, crystal fields (Dq), inter-electronic repulsion parameters (B, C) were evaluated. By correlating optical and EPR spectral data, the site symmetry of Co(2+) ion in the host lattice was determined as octahedral. Photoluminescence spectra exhibited the emission bands in ultraviolet and blue regions. The CIE chromaticity coordinates are also evaluated from the emission spectrum. FT-IR spectra showed the characteristic vibrational bands of Zn-O.

Mixed alkali effect and optical properties of Ni2+ doped 20ZnO + xLi2O + (30 − x)Na2O + 50B2O3 glasses

Optical and physical properties of Ni2+ doped 20ZnO+xLi2O+(30-x)Na2O+50B2O3 (5≤x≤25) glasses are carried out at room temperature. Powder XRD pattern of all the glass samples confirms the amorphous nature. Several physical parameters are evaluated for all the glasses with respect to the composition. The optical absorption spectra confirm the site symmetry of the Ni2+ doped glasses are near octahedral. Crystal field and inter-electronic repulsion parameters are also evaluated. It is interesting to observe that the optical band gap and Urbach energies exhibit the mixed alkali effect. The FT-IR spectral investigations of Ni2+ doped glasses exhibit characteristic vibrations of BO3 and BO4 units.

Mixed alkali effect in Mn2+ doped 20ZnO+xLi2O+(30-x)K2O+50B2O3(5≤x≤25) glasses.

Divalent Mn2+ ions containing 20ZnO+xLi2O+(30-x)K2O+50B2O3(5≤x≤25) mol% glasses are prepared by using melt quench technique and are characterized by several spectroscopic techniques. Various physical parameters are evaluated from the measured values of density and refractive index for the observation of mixed alkali effect. Structural changes of Mn2+ doped ZLKB glasses are investigated by Powder XRD, UV-VIS absorption, Electron Paramagnetic Resonance and FT-IR spectroscopic studies. The XRD pattern indicates the amorphous nature of prepared glasses. FT-IR measurements of all glasses revealed that the network structure of glass system are mainly based on BO3 and BO4 units placed in different structural groups in which the BO3 units being dominant. The EPR spectra of Mn2+ ions doped glasses exhibited a characteristic hyperfine sextet around g=2.0. The spectroscopic analyses of the obtained results confirmed near octahedral site symmetry for the Mn2+ impurity ions. Crystal field and Racah parameters are evaluated from optical absorption spectra. The optical band gap and Urbach energies are determined which exhibited the mixed alkali effect.

Structural and optical investigations on ZnCdO nanopowder

ZnCdO nanocrystalline powder is synthesized by the simple solution method at room temperature. Synthesized powder was characterized by powder x-ray diffraction (XRD), scanning electron microscope with x-ray spectrometry (EDX), thermo gravimetry?differential thermal analysis (TG?DTA) and other spectroscopic techniques. The XRD pattern exhibited a mixture of hexagonal ZnO and cubic cadmium oxide phases. The crystallite size of the prepared powder was found to be around 28?nm. Surface morphology of sample was determined by scanning electron microscopy and the distribution of Zn, Cd and oxygen species in the prepared sample was identified by chemical composition mapping through EDX. TG?DTA curves indicate the thermal stability of the prepared sample. The photoluminescence spectrum shows the bands in ultra-violet and blue emission regions. The Fourier transform infrared spectrum demonstrates the presence of metal oxide vibrations.

Synthesis and spectral characterizations of trivalent ions (Cr3+, Fe3+) doped CdO nanopowders

Trivalent transition metal ions (Cr(3+), Fe(3+)) doped CdO nanopowders via sonication in the presence of Sodium lauryl sulfate as stabilizing agent were synthesized and characterized. Powder XRD studies indicate that the obtained CdO has a cubic phase and concluded that the trivalent ions doping induced the lattice constants to change some extent. Optical absorption spectra exhibited the characteristic bands of Cr(3+) and Fe(3+) ions in octahedral site symmetry. Crystal field (Dq) and inter-electronic repulsion (B and C) parameters are evaluated for Cr(3+) doped CdO nanopowders as Dq=1540, B=619 and C=3327 cm(-1) and for Fe(3+) doped CdO nanopowders Dq=920, B=690, C=2750 cm(-1). EPR spectra of the Cr(3+) and Fe(3+) doped CdO nanopowders exhibited resonances at g=1.973 and g=2 respectively which indicate distorted octahedral site for both ions with the host. Photoluminescence spectra shows the emission bands in violet and bluish green regions for Cr(3+) doped CdO, ultraviolet and blue emissions for Fe(3+) doped CdO nanopowders. The CIE chromaticity coordinates were also evaluated from the emission spectrum. FT-IR spectra indicate the presence of various functional groups of host lattice.

Synthesis and spectroscopic characterization of Mn(II) doped organic amine templated chlorocadmiumphosphate CdHPO4Cl · [H3N(CH2)6NH3]0.5 crystals

Chlorocadmiumphosphate CdHPO4Cl · [H3N(CH2)6NH3]0.5 crystals doped with Mn(II) are grown at room temperature via organic amine template method and characterized by spectroscopic techniques to obtain information on the nature of the incorporated Mn(II). Powder X-ray diffraction patterns of the sample are indexed to monoclinic cell and average crystalline size is found to be around 55 nm. The optical absorption spectrum exhibits various bands which are characteristic of Mn(II) in distorted octahedral site symmetry, confirmed by characteristic resonance signal at g = 2.018 observed in the EPR spectrum. Fourier transform infrared spectrum shows the specific vibrations of phosphate and organic molecules. Thermal curves indicate that the crystal is stable at 307°C; above this temperature crystal structure disintegrates due to removal of the organic amine template.

Spectral investigations of Cu2+ doped beta-barium borate nanopowder by the co-precipitation method

A Cu2+ doped beta-barium borate nanopowder has been synthesized using the co-precipitation method. The average crystallite size of the present system is evaluated at 68 nm and the lattice cell parameters are calculated from x-ray diffraction data. Optical absorption spectral data reveal that the Cu2+ ions are in a tetragonally distorted octahedral site in the host lattice. Direct, indirect and Urbach energies are calculated with the absorption edge technique. Electron paramagnetic resonance results confirm that the Cu2+ ions enter a tetragonally elongated octahedral site at room temperature. The crystal field and spin-Hamiltonian parameters are also evaluated. Fourier transform infrared spectroscopy confirms the vibrational bands of Ba–O and B–O in the system.

Synthesis and spectroscopic characterization of Cu(II) containing chlorocadmiumphosphate Cd(HPO4)Cl·[H3N(CH2)6NH3]0.5 crystals

Chlorocadmiumphosphate Cd(HPO(4))Cl·[H(3)N(CH(2))(6)NH(3)](0.5) crystals containing Cu(II) ions have been successfully synthesized at room temperature by using organic amine 1,6-diamino hexane as a template. The samples are characterized by X-ray powder diffraction, Thermal and spectroscopic studies. These are crystallizes in the monoclinic crystal system with cell dimensions: a=1.7697, b=0.6576, c=1.9026nm and β=106.5°. FT-IR spectrum showed the absorption bands related to PO(4), NH(3)(+) ions and other organic molecule vibrations originated from the templated molecule. The prepared crystals are stable at room temperature and as well as up to around 300°C which were confirmed by thermal analysis. Optical absorption and EPR studies suggest that Cu(II) ion enters in to the lattice as tetragonally distorted octahedral symmetry, for which crystal field and spin-Hamiltonian parameters are calculated. Bonding parameters are suggesting that there exists partial covalent nature between Cu(II) ions and ligands.

Synthesis and spectral investigations of Cu(II) ion-doped NaCaAlPO4F3 phosphor

Cu(II) ion-doped NaCaAlPO(4)F(3) phosphor has been synthesized using a solid state reaction method. The prepared sample is characterized by powder X-ray diffraction, scanning electron microscope, optical absorption, electron paramagnetic resonance photoluminescence and Fourier transform infrared spectroscopy techniques. The crystallite size evaluated from x-ray diffraction data is in nanometers. Scanning electron microscopy micrographs showed the presence of several irregular shaped particles. From optical absorption and electron paramagnetic resonance spectral data the doped Cu(II) ions are ascribed to distorted octahedral site symmetry. The synthesized phosphor exhibits emission bands in ultraviolet, blue and green regions under the excitation wavelength of 335 nm. The CIE chromaticity coordinates (x = 0.159, y = 0.204) also calculated for the prepared sample from the emission spectrum. The Fourier transform infrared spectroscopy spectrum revealed the characteristic vibrational bands of the prepared phosphor material.