A. V. Nikol’skii

Electronic structure of bismuth ferrite and hematite single crystals: X-ray photoelectron study and calculation

The X-ray photoelectron spectra of the inner levels and valence bands of the surfaces of BiFeO3 and Fe2O3 single crystals have been measured using X-ray photoelectron spectroscopy on an ESCALAB 250 X-ray photoelectron microprobe with monochromatization of X-ray radiation of the AlKα line. The ab initio calculations have been performed by the full-potential pseudopotential method in terms of the density functional theory (Quantum-Espresso program package). The band structure and the total and partial densities of states have been calculated for the BiFeO3 and Fe2O3 systems. A comparison of the theoretical and experimental results has demonstrated good agreement between theory and experiment.

Valence state of manganese ions in the La1−α BiLaβMnLa1−δ OLa3±γ ceramics

The valence state of the Mn ions in ceramic samples of the La1−α BiLaβMnLa1−δ OLa3±γ composition (LBMO) has been studied using the X-ray photoelectron spectroscopy. The presence of Mn3+ and Mn4+ ions in these compounds has been shown. The relative content Mn3+/Mn4+ has been determined by means of fitting the experimental Mn 2p spectra by the superposition of theoretical spectra of Mn3+ and Mn4+ ions. The elemental composition of the samples has been determined by the X-ray photoelectron spectroscopy and electron probe microanalysis. It has been established that the relative content of Mn4+ ions correlates with parameter δ, which characterizes the deviation of the actual elemental composition of the La1−α BiLaβMnLa1−δ OLa3±γ ceramics from stoichiometry La1 − xBixMnO3.

Temperature dependence of the concentration of surface phases in a BaTiO3 single crystal according to X-ray photoelectron spectroscopy data

The composition of the surface and the chemical bonding are studied by X-ray photoelectron spectroscopy (using an ESCALAB 250 instrument) in a BaTiO3 single crystal within the temperature range of T = 296–573 K. The evolution of the surface Ba-O phase is found to be reversible in this temperature range.

Electronic structure of a PbFe1/2Nb1/2O3 single crystal in the ferroelectric and paraelectric states, according to X-Ray photoelectron spectroscopy data and first principle calculations

Electronic structure of the PbFe1/2Nb1/2O3 single crystal is studied by means of X-ray photoelectron spectroscopy on an ESCALAB 250 system and first principle FEFF9 at temperatures of 296 and 403 K.

The dynamics of 180° domains in a ferroelectric in the process of polarization reversal and electron emission

A model is proposed to describe the evolution of 180° domains in a ferroelectric. Closed analytic expressions are obtained for the velocity of sideways motion of a 180° domain wall in an electric field and numerical calculations are performed. The connection between polarization reversal and electron emission is discussed.

Electron-beam-induced polarization of lithium- and manganese-modified lead ferroniobate ceramics and its respective emission phenomena

A polarization state is formed with an electron beam in ceramic samples of pure lead ferroniobate (PFN) and PFN modified to a superstoichiometric composition at the stage of synthesis by adding 1 wt % lithium carbonate (PFNL) and 1 wt % of magnesia (PFNM). It is shown that in the case of PFNL, polarization by an electron beam is more efficient than the conventional method of “hot” polarization. Reasons for the observed effects, including enhanced electron emission from local irradiated areas on the surface of the ceramics, are discussed.

Anomalous electron emission spectra and polarization phenomena in a lead magnesium niobate single crystal

The time dependences of the intensity and the energy positions of fine-structure of the spectra of anomalous electron emission from a polarized lead magnesium niobate (PMN) single crystal irradiated with soft x-rays are investigated experimentally. It is shown that the relaxation time of the electret charge can be determined from the graphs of these dependences, and the depth distribution of the potential in the surface layer of the sample can be determined from the profile of the anomalous electron emission spectrum. Estimates of the fields in the surface layers of a polarized PMN single crystal, obtained from the characteristics of the anomalous electron emission spectra, agree with data obtained by electrophysical research techniques.

X-ray photoelectron and mössbauer spectroscopy studies of the valence state of transition metal ions in Co1–xFexCr2O4 (x = 0.1, 0.2, 0.5) ceramics

The valence state of transition metal ions in the Co1–xFexCr2O4 (x = 0.1, 0.2, 0.5) system has been investigated using X-ray photoelectron and Mössbauer spectroscopy. It has been shown that, in this system, there are Fe2+ and Fe3+ ions. The relative Fe3+/Fe2+ contents have been determined by fitting the experimental Fe 2p photoelectron spectra by a superposition of theoretical spectra of the Fe2+ and Fe3+ ions, as well as using Mössbauer spectroscopy.

Effects of doping of lead titanate with alkaline-earth elements

Solid solutions of the (