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Epitaxial thin films of Fe doped SrTiO3 have been studied by the use of resonant photoemission. This technique allowed us to identify contributions of the Fe and Ti originating electronic states to the valence band. Two valence states of iron Fe2+ and Fe3+, detected on the base of x-ray absorption studies spectra, appeared to form quite different contributions to the valence band of SrTiO3. The electronic states within the in-gap region can be attributed to Fe and Ti ions. The Fe2+ originating states which can be connected to the presence of oxygen vacancies form a broad band reaching binding energies of about 0.5 eV belowthe conduction band, while Fe3+ states form in the gap a sharp feature localized just above the top of the valence band. These structures were also confirmed by calculations performed with the use of the FP-LAPW/APW+lo method including Coulomb correlations within the d shell. It has been shown that Fe doping induced Ti originating states in the energy gap which can be related to the hybridization of Ti and Fe 3d orbitals. [ABSTRACT FROM AUTHOR]

Epitaxial thin films of Fe doped SrTiO3 have been studied by the use of resonant photoemission. This technique allowed us to identify contributions of the Fe and Ti originating electronic states to the valence band. Two valence states of iron Fe2+ and Fe3+, detected on the base of x-ray absorption studies spectra, appeared to form quite different contributions to the valence band of SrTiO3. The electronic states within the in-gap region can be attributed to Fe and Ti ions. The Fe2+ originating states which can be connected to the presence of oxygen vacancies form a broad band reaching binding energies of about 0.5 eV below the conduction band, while Fe3+ states form in the gap a sharp feature localized just above the top of the valence band. These structures were also confirmed by calculations performed with the use of the FP-LAPW/APW+lo method including Coulomb correlations within the d shell. It has been shown that Fe doping induced Ti originating states in the energy gap which can be related to the hybridization of Ti and Fe 3d orbitals. [ABSTRACT FROM AUTHOR]

In many cases, functionality is connected with the response of a material to the action of an external electric field. In oxidic perovskites, so widely used in practice, a disadvantage is their surface chemical instability when subjected to an electric field. That is why investigations of the influence of a high intensity alternating electric field on the phase transition temperatures and chemical properties of the surface and bulk of single crystals of PbZrO3 intentionally made defective by doping with niobium have been undertaken. It has been demonstrated that defects produced through the electro-degradation process make the low-field dielectric response a highly diffusive one, but they do not obscure the sharp phase transitions detected by temperature changes in the bulk piezoelectric and electrostrictive deformation around the critical temperature. Based on XPS spectra, the types of defects at the surface and in the bulk of as-grown single crystals caused by the electric field action are identified. It has been shown that the surface–bulk interrelation in ferroic lead zirconate and solid solutions based on this material has to be taken into account while trying to use them as high quality functional materials. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy has been applied to study the electronic structure of the epitaxial Fe-doped SrTiO3 thin films with an Fe concentration of 1 and 2 at%. The results were compared to undoped thin films and lightly Fe-doped single crystal of SrTiO3. Fe doping was found to increase the amount of the in-gap states which can be related to the increased ability of Fe-doped thin films to exhibit resistive switching behaviour. Core level analysis indicates the mixed-valence character of Fe atoms in the films, with a divalent contribution situated on the surface. [ABSTRACT FROM AUTHOR]

The process of ionic segregation in the surface layer induced by the thermal treatment of the NaNbO3 crystal was studied. The study of the as grown crystal and the crystal heated at 970 K in ambient air was carried out for comparison. The changes in the concentration of the elements within the surface layer were determined using XPS measurements. The AFM technique was applied to determine the surface morphology related to nano-scale transformation. The possibility of appearance of the Ruddlesden-Popper phases was detected by the XRD test. The change in the features of the electric permittivity, the loss tangent, and the electric conductivity was ascribed to the marked participation of the chemically modified surface layer in the measured effective electrical properties. [ABSTRACT FROM AUTHOR]

One-dimensional transition metal materials are promising supports for precious metals used in energy production processes. Due to their electrochemical properties, 3d-group metals (such as Ni, Co, and Fe) can actively interact with catalysts by a strong metal-support interaction. This study shows that changing the Ni:Co ratio makes it possible to modulate the structure of the catalyst supports, which, in turn, provides a tool for designing their electrical and electrochemical properties. For example, Ni 1 -Co 9 shows the highest electrical conductivity (5.8-10 -4 S/cm) among all of the materials examined. On the contrary, the Pd@Ni 7 -Co 3 system presents the highest mass activity (>2000 mA mg -1 ) at 0.7 V, exceeding by several times that of commercial Pt/C (>300 mA mg -1 ) at the same potential. Our study opens the gateway for applications of bimetallic transition metal nanowires in catalytic conversion and energy production processes.