We report the synthesis of CuO nanoparticles using different solvents by a low cost sol-gel route. Evolution of structure, microstructure and optical absorption analysis of these nanoparticles were studied using X-ray diffraction (XRD) and UV-Visible spectrophotometer. XRD analysis indicated that the crystallite size and strain are higher for the CuO nanoparticle synthesized using propanol as solvent. Optical absorption analysis indicated the red shift of indirect band gap and the blue shift of direct band gap. In the present case, red shift is associated with the formation of surface defects whereas the blue shift is due to the quantum confinement effect seen for nanoparticle systems.

: Mott-Hubbard anti-ferromagnetic insulator, NiO shows p-type semiconducting behaviour due to vacancy at Ni 2+ site in its bunsenite structure. We report the modification of structural and magnetic order in NiO on Fe doping. NiO samples at different Fe concentrations in the range 0 to 5 at.% have been prepared by chemical co-precipitation and post thermal decomposition method. Both structural and magnetic characterization reveal that with increasing Fe doping concentration, NiO evolves as a magnetically inhomogeneous state out of the parent homogeneous antiferromagnetic state. In addition, structural inhomogeneity was also observed with Fe precipitating to γ-Fe 2 O 3 phase, the signature of which could be clearly seen for Fe content beyond 2 at.%. At lower Fe content however, some amount of Fe occupies lattice and interstitial sites in the NiO matrix and drive the latter to acquire ferromagnetic ordering, which was evident from a clear hysteresis loop at 300 K.

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We present a brief review on the evolution of structure, microstructure, electrical and magnetic properties of NiO with transition metal (TM) doping. The fcc structure of NiO is not affected with TM doping whereas the some of the TM ion influences the microstructure. The antiferromagnetic property of NiO is strongly modified with some of the TM (Fe, Mn, V) doping and the same is not much affected with some other TM (Co, Cr, Zn and Cu) doping. Not only the dopants but also the form of the material decides the magnetic order in the host matrix. Powder NiO exhibits room temperature ferromagnetism with Fe doping, superparamagnetism with Mn doping. NiO thin films on the other hand exhibit ferromagnetism with Fe, Mn and V doping. The ferromagnetic ordering in these cases was improved with Li co-doping. The increased ferromagnetism in these cases may be due to increase of hole concentration due to Li doping. Giant dielectric response has been observed for (Li, Fe) and (Li, V) doped NiO ceramics.

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We report in situ x-ray diffraction (XRD) study of 200 MeV Ag ion irradiation induced structural modification in c-axis oriented YBa2Cu3O7−y (YBCO) thin films at 89 K. The films remained c-axis oriented up to a fluence of 2×1013 ionscm−2, where complete amorphization sets in. The amorphous ion tracks, the strained region around these tracks, and irradiation induced point defects are shown to control the evolution of the structure with ion fluence. Secondary electrons emanating from the ion paths are shown to create point defects in a cylindrical region of 97 nm radius, which corresponds to their maximum range in the YBCO medium. The point defects are created exclusively in the CuO basal planes of fully oxygenated YBCO, which has not been possible, by other techniques including low energy ion irradiation and thermal quenching. The point defects led to a faster decrease in the integral intensity of XRD peaks at very low fluences of irradiation (Φ≤3×1010 ionscm−2) than what can be expected from amorphous tracks. The radius of amorphous ion tracks, estimated from the fluence dependence of integral XRD peak intensity beyond this fluence, was found to be 1.9 nm. Both point defect and the strained region around amorphous ion tracks are shown to contribute to the increase in the c-parameter at 89 K. The full width at half maximum (FWHM) of XRD peaks arising mostly due to the strained region around the ion tracks showed an incubation effect up to 1012 ionscm−2, before increasing at higher fluences. Fluence dependence of FWHM gives the cross section of the strained region as 37.9 nm2, which is more than three times the cross section of the amorphous ion tracks.

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