ABSTRACT
Metal transition doped oxide thin films or nanocomposites have recently emerged at the forefront of potentials research. With the focus mainly on efficiency, the aspect of stability against optical irradiation of such materials has so far not been thoroughly addressed. This work covers the synthesis of silver doped lanthanum oxide thin films (La2O3:Ag) which have been prepared by the spray pyrolysis technique on glass substrates at 460°C. Then, Ag thin films were grown on lanthanum oxide thin films by thermal evaporation. The present work aims to reach the synthesis of La2O3:Ag thin films using both the spray pyrolysis and thermal evaporation techniques. First, X-ray diffraction analysis shows that undoped and Ag doped films crystallize in a mixture of hexagonal and cubic phase with crystallites oriented along (001) direction. Raman spectroscopy shows the bands positions corresponding to hexagonal and cubic phases. On the other hand, an attempt regarding their optical properties has been carried out by means of photoluminescence measurements. Second, from electrical conductivity measurements, the activation energy decreases from 1.42 to 1.09eV with the increase of annealing time and the charge carriers are following the CBH model as dominant charge transport mechanism. Finally, the annealing time influences the surface wettability property and transforms La2O3 character from hydrophobic (θ>90°) to hydrophilic (θ<90°).
ABSTRACT
Nanostructured Fe-8P (wt%) powder mixture was prepared by high energy ball milling in a planetary ball mill (Fritsch P7) under argon atmosphere. The morphology of the particles, the phase identification and the alloying evolution process as a function of milling time are studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and 57Fe Mössbauer spectrometry (MS), respectively. Refinement based on Rietveld method of the XRD patterns and the Mössbauer spectra analysis show that the Fe(x)P (1 < x < 2) and Fe2P phosphide phases are the main product after 3 h of milling (approximately 10%). From the XRD Rietveld refinement, it is observed that the Fe2P phase disappears completely after 12 h of milling, while the Fe3P nanophase appears after 9 h and remains for larger milling duration. The lattice structure distortion is evidenced by the lattice parameter changes of the milled products. A two structure state of the alpha-Fe(P) solid solution: alpha-Fe1 and alpha-Fe2 is confirmed by both the XRD and MS measurements. After milling for 21 h, a mixture of a disordered two phase alpha-Fe(P) solid solution, Fe3P nanophase and a small amount of a paramagnetic FeP phosphide phase (approximately 2%) is obtained.
