Layered nanocomposites of V1.67Ti0.33O 5±δ ·nH2O gels are synthesized by using sol-gel technology. Then an aqueous solution of hydroquinone (HQ) was mixed with the formed gel in molar ratio 0.33 : 1 and 0.17 : 1 respectively. In this way the V1.67Ti0.33O 5±δ ·nH2O / 2HQ and V1.67Ti0.33O 5±δ ·nH2O / HQ gels were synthesized. The valences of vanadium and titanium ions in the investigated compounds are studied by means of X-ray photoelectron spectroscopy (XPS) before and after etching the samples with Ar + ions for 15 min (3 keV, current density 10 µA cm −2 ). XPS analysis results show that independent of the hydroquinone intercalation degree (one or two hydroquinone) and Ar + ion etching the ions of titanium are in stable 4+ states. Vanadium ions in all cases (one or two hydroquinone, before and after etching) are in V 3+ , V 4+ , and V 5+ states. The increase in quantity of hydroquinone in the samples leads to higher concentration of V 3+ and V 4+ ions. The concentrations of lower valence vanadium ions increase after Ar + ion etching of the samples.
Thin LaNiO 3−δ films with pseudocubic (100) preferred orientation were prepared by reactive DC magnetron sputtering and in situ annealed in O2 and vacuum. X-ray photoelectron spectroscopy (XPS) was used to determine the variation in composition of the films under high temperature annealing. The experimental O 1s and La 3d -Ni 2p 3/2 spectra of LaNiO 3−δ films was analysed in terms of O 2− , O − /(OH) − , and weakly adsorbed oxygen species. It was shown that the change in the type of conductivity from metallic to semiconducting one is accompanied by a marked increase in the intensity of the lateral (∼531 eV) peak of oxygen. The quantitative analyses of La 3d -Ni 2p 3/2 spectra show that the Ni/La concentration ratio significantly decreases after heating above the dehydration temperature. These variations in conductivity and surface composition were attributed to the loss of lattice oxygen with subsequent adsorption of O − and (OH) − anions and weakly adsorbed oxygen species from ambient air.
La 2 O 3 thin films were prepared by a sol-gel method and annealed in air and vacuum at various temperatures. The X-ray photoelectron spectroscopy (XPS) was used to investigate the properties and composition of films. The La 3d and O 1s spectra of films were analysed. It was shown that oxygen ions in La 2 O 3 are in two states-O 2anions connected with lanthanum, and oxygen in the (OH)group. The thermal transformation of lanthanum hydroxide to oxide process was triggered by thermal treatment at temperatures above 600 K. It was shown that after annealing thin films for longer time intervals in vacuum the intensity of O 2component increases and the intensity of oxygen in (OH)decreases. The drop of oxygen in the (OH)group was attributed to dehydration process.
A vanadium – hydroquinone oxide bronze has been synthesized by using a sol gel technology. The V2O5 powder, hydrogen peroxide, and hydroquinone C6H4(OH)2 were used as the starting materials to produce the bronze. At first the vanadium gel was made by the dissolving of vanadium pentoxide powder in hydrogen peroxide at 273 K. Then the solution was heated up to 350 K for the dissociation of peroxide complexes. An aqueous solution of hydroquinone was mixed with the formed gel in molar ratio 0.33:1. In this way the V2O5±δ·nH2O/HQ (HQ‐hydroquinone) gel was synthesized. These gels are applied on the Ni pad and dried in an air (wet gel synthesis) or heated up to 580 K in air for 1 h for the water removal from gel (bronze production). The wet gel, as well as a bronze, was investigated by means of XPS method. Analysis of V‐O region of XPS spectra shows that vanadium in both cases (wet gel and bronze) is in stable V5+ state. Oxygen in wet gel can be associated with V ions, hydroxide group and water. In bronze oxygen is connected with V and hydrogen (hydroxide). (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
We present a theoretical and experimental study of the electronic structure of SrRuO 3 after introduction of vacancies. Theoretically, the modeling of non-stoichiometric variations of SrRuO 3 was performed by removing appropriate atoms or their combinations, whereas in the experiments the annealing treatment at moderate temperatures in ultra-high vacuum was applied. At comparison of the obtained results allows us to draw an important conclusion that the formation of oxygen vacancies may be closely related to the manifestation of strong correlation effects in SrRuO 3 .
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