Alessandro Galenda

La0.6Sr0.4Co0.8Fe0.2O3-δ and Fe2O3/La0.6Sr0.4Co0.8Fe0.2O3-δ Powders: XPS Characterization

Perovskite based oxides have been attracting great interest because of the possible applications in several technological fields such as energy production and gas sensing. The present work focuses on the XPS analysis of three perovskite-based powders: the first is a nanosized La0.6Sr0.4Co0.8Fe0.2O3-δ (LaSrCoFeO) system; the other two are Fe2O3/LaSrCoFeO nanocomposite powders which differ in the amount of deposited Fe2O3. The nanosized LaSrCoFeO perovskite was obtained by the Pechini method and treated at 1173 K for 26 h. Nanocomposite Fe2O3/LaSrCoFeO powder samples (Fe2O3/LaSrCoFeO = 1:9 and 1:1 wt) were obtained by wet impregnation.

PrMnO3 Prepared by the Citrate Gel Method, Studied by XPS

In the present work a praseodymium manganite powder synthesized by means of the citric acid method is investigated by means of XPS. Besides the wide scan spectra, detailed spectra for the Pr 3d, Pr 4d, Mn 2p and O 1s regions and related data are presented and discussed. The praseodymium peaks position and shape suggest the presence of Pr(III) in oxide systems; Mn 2p peak is consistent with the presence of Mn(III) and/or Mn(IV) in oxides. The Pr/Mn atomic ratio ranges around 1; the O/(Pr+Mn) atomic ratio is higher than the expected value confirming the surface hydroxylation and carbonation.

From La2O3 To LaCoO3: XPS Analysis

Nanostructured LaCoO3 powder was prepared by a new approach: cobalt oxide nanoparticles were deposited, by wet impregnation, on the La2O3 surface. The La2O3 support was prepared by precipitation from a basic solution of La(NO3)3⋅6H2O. The precipitate was dried at 353 K for 2 h and calcined at 923 K for 6 h in air. Nanostructured LaCoO3 was obtained by wet impregnation of La2O3 with aqueous solutions of Co(NO3)2⋅6H2O: [Co/La]nomimal = 1.0 (nominal atomic ratio is obtained from the precursors weighed quantities). The obtained suspension was maintained under stirring for two days and then kept in rest for one day. Water was evaporated in air and the obtained solid was dried at 353 K for 2 h and at 923 K for 6 h in air. The thermal treatment in air promotes a solid state reaction between La-O and Co-O and then the formation of LaCoO3.

CuO/CeO2 Nanocomposites: An XPS Study

CuO/CeO2 nanocomposite powders were prepared by wet impregnation of nanosized ceria powders. The samples are characterized by a nominal (i.e. calculated from the weighted amount of precursors) Cu/Ce atomic ratio: 0.05 (Accession #1081), 0.1 (Accession #1082), 0.2 (Accession #1083), 0.35 (Accession #1084) and 0.5 (Accession #1085). The surface properties and the influence of the Cu/Ce atomic ratio are investigated by means of XPS. Besides the wide scan spectra, detailed spectra for the Ce 3d, Ce 4d, Cu 2p and O 1s regions and related data are presented and discussed. XP analysis reveals the presence of CuO; in the samples with lower Cu/Ce atomic ratio traces of Cu2O are also evident. The surface Cu/Ce atomic ratio obtained from XPS data is always higher than the nominal one suggesting the surface segregation of copper.

LaMnO3: Influence of the Addition of Ba and Sr

The present work focuses on lanthanum manganite-based materials obtained by citrate (LaMnO3 and La0.6Sr0.4MnO3) and Pechini (La0.6Ba0.4MnO3) methods. The influence of the addition of barium and strontium is studied. The surface properties of LaMnO3, La0.6Ba0.4MnO3 and La0.6Sr0.4MnO3 powders are investigated by means of XPS using a standard Al Kα source. Besides the wide scan spectra, detailed spectra for the La 3d, Mn 2p, O 1s, Sr 3d and Ba 3d regions and related data are presented and discussed.

La2Cu0.8Co0.2O4+δ by Pechini Method

Cobalt-doped lanthanum cuprates of the type La2Cu1-xCoxO4 are Ruddlesden-Popper compounds characterized by several interesting properties. In particular, thanks to the presence of copper and cobalt, they can be utilized as catalysts in redox reactions. Moreover, from an electrical point of view, cobalt-doped lanthanum cuprates are Mixed-Electronic-Ionic-Conductors. These important characteristics could be gainfully employed in improving the Intermediate-Temperature-Solid-Oxide-Fuel-Cells electrodes performances, from both the catalytic and electrical sides. A La2.0Cu0.8Co0.2O4+δ powder was prepared by Pechini procedure. Besides the wide scan spectra, detailed spectra for the La 3d, La 4d, Cu 2p, Co 2p, O 1s and C 1s regions and related data are presented and discussed. XP analysis confirms the presence of La (III) and Cu (II); the peak shapes are consistent with a residual presence of hydroxide and carbonate species, as confirmed by the O 1s and C 1s signals. The XPS atomic composition supports this hypot...

Mixed Magnesium and Zinc Oxide Prepared by Co-precipitation and Analyzed by XPS

Two Zinc-Magnesium Oxide powders were prepared by means of a sol-gel method based on the mixing of nitrates of Mg and Zn, followed by complexation with citric acid. The samples are characterized by a nominal (i.e. calculated from the weighted amount of precursors) Zn/Mg atomic ratio of 0.01 (specimen 1, Accession #1232), and 0.5 (specimen 2, Accession #1233). The surface properties and the influence of the Zn/Mg atomic ratio are investigated by means of XPS (using a standard Al Kα). Besides the wide scan spectra, detailed spectra for the Mg 1s, Zn 2p3/2 and O 1s regions and related data are presented and discussed. XP analysis confirms the presence of Mg (II) and Zn (II). The XPS Zn/Mg atomic ratio is always lower than the nominal one; this is particularly evident in specimen 1 (Accession #1232) thus suggesting a certain surface segregation of magnesium. The O/(Mg + Zn) atomic ratio is higher than the nominal one and decreases with increasing the Zn/Mg atomic ratio (from 1.5 for [Zn/Mg]nom = 0.01 to 1.3 f...

CuO/MgO Nanocomposites by Wet Impregnation: An XPS Study

Zinc oxide/magnesium oxide nanocomposite powders were prepared by wet impregnation of nanosized magnesia powders. The supporting magnesia was obtained by precipitation from a solution of magnesium nitrate. The samples are characterized by a nominal (i.e. calculated from the weighted amount of precursors) Zn/Mg atomic ratio of 0.01 (Accession #1189), 0.1 (Accession #1190), 0.25 (Accession #1191), and 0.5 (Accession #1192). The surface properties and the influence of the Zn/Mg atomic ratio are investigated by means of XPS (using a standard Al K α ). Besides the wide scan spectra, detailed spectra for the Mg 1s, Zn 2p3/2 and O 1s regions and related data are presented and discussed. XPS analysis confirms the presence of MgO and ZnO; the peak shapes are consistent with a more heterogeneous situation for the samples with lower Zn/Mg atomic ratios. The XPS Zn/Mg atomic ratio increases with increasing the nominal Zn/Mg atomic ratio reaching a plateau (of about 0.70) for the [Zn/Mg]nom = 0.25. The decrease of the O/(Mg+Zn) atomic ratio observed with increasing the Zn/Mg one (from 2.5 for [Zn/Mg]nom = 0.01 to 1.9 for [Zn/Mg]nom = 0.5) suggests a lower reactivity of ZnO with respect to atmosphere. This result is confirmed by the O 1s peak shape evolution.

Diblock and Triblock Fluorinated Copolymers: An ARXPS Study

In this contribution we prepared (by TEMPO-mediated radical polymerization) two triblock copolymers (poly(S-b-SF8-b-SP3) and poly(S-b-SP3-b-SF8)) of the A-B-C and A-C-B types composed of hydrophobic styrene (A), hydrophobic/lipophobic fluorinated styrene (B), and hydrophilic PEG-modified styrene (C) polymer blocks with greatly varied degrees of polymerization. A diblock copolymer (poly(S-b-SF8)) was used for comparison. The resulting surface structure and organization of the polymer films were investigated by x-ray photoelectron spectroscopy at different angles (70°, 50°, and 20° being the angle between the analyzer axis and the specimen normal). Besides the wide scan spectra, detailed spectra for the C 1s, F 1s and O 1s regions and related data are presented and discussed. XPS analysis reveals the preferential surface segregation of the phase-separated fluorinated block regardless of the distinctly different macromolecular architectures of the triblock copolymers.

Influence of Sr and Fe Dopants on the Surface Properties of LaGaO3

LaGaO3 doped on A-site and B-site with different amounts of strontium and iron, respectively (La0.8Sr0.2GaO3-δ, La0.6Sr0.4GaO3-δ and LaGa0.8Fe0.2O3, LaGa0.4Fe0.6O3) as well as a doubly doped LaGaO3 perovskite (La0.8Sr0.2Ga0.8Fe0.2O3-δ) have been synthesized by citrate gel method. The present work focuses on the XPS analysis. In particular, the effects of dopants and dopant concentrations on the LaGaO3 surface properties have been investigated and discussed. Besides the wide scan spectrum, detailed spectra for the La 3d, Ga 2p3/2, Sr 3d, Fe 2p, O 1s and C 1s regions and related data are presented and discussed.