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Polycrystalline Pr 1- x Ca x MnO 3 ( х = 0.3, 0.35, 04, 0.45, and 0.5) samples are synthesized by solid-state reaction method. Crystal structure of the samples is studied by X-ray diffraction method with Rietveld refinement. Diffraction patterns from all the samples are well indexed within the Pnma space group. It is shown that lattice parameters and unit cell volume decrease monotonically and O−Mn−O angles become closer to the ideal 180⁰ value upon the growth of x . Mn2p, Mn3s, Ca2p, Pr3d, Pr4d, and O1s X-ray photoelectron spectra are measured. Pr3d and Pr4d spectra are calculated in isolated ion approximation with approximate accounting for the charge transfer effect. Elemental compositions of samples are measured by the XPS method; they differ noticeably from the nominal ones. Charge compensation upon heterovalent Pr 3+ → Ca 2+ substitution is shown to realize via two mechanisms: creation of oxygen vacancies and formation of Mn 4+ ions coexisting with Mn 3+ . Relative Mn 4+ /Mn 3+ abundances are determined via decomposition of Mn2p and Mn3s XPS into contributions from the spectra of tri- and quadrivalent Mn ions. The amount of Mn 4+ ions is shown to increase with Ca content x . [ABSTRACT FROM AUTHOR]

An integrated study of samples of Bi 1− х Ca х FeO 3- δ (BCFO) system for 0 ≤ x ≤ 1 (step 0.1) is performed using X-ray diffraction (XRD), Raman scattering, Mössbauer spectroscopy, and X-ray photoelectron spectroscopy (XPS). Measured elemental compositions of samples were found to deviate substantially from nominal ones. X-ray structure analysis discovered a continuous series of solid solutions with perovskite structure (or its derivatives) on the interval of nominal Ca content 0 ≤ x ≤ 0.9. However, the analysis of the data from all the methods used, limits the region of single phase samples (in presence of insignificant amount of foreign ones) to nominal Ca content interval 0.1 < x < 0.4. No Fe 4+ ions are discovered upon substitution of Bi 3+ by Ca 2+ , neither by Mössbauer spectroscopy, nor by XPS. Charge compensation in Bi 1− х Ca х FeO 3- δ takes place mostly via creation of oxygen vacancies. Charge transfer satellites position in Ca2p XPS is shown to be sensitive to a number of oxygen ions in the immediate environment of Ca. [ABSTRACT FROM AUTHOR]

Ceramics with nominal composition Co 1− x Fe x Cr 2 O 4 ( x = 0.1, 0.2, 0.5) are synthesized via a solid state reaction method. Crystal structure of samples is studied with X-ray diffraction. Actual elemental composition is determined using X-ray microanalysis and X-ray photoelectron spectroscopy (XPS). Samples’ morphology is studied with scanning electron microscopy. Valence state of the Co, Fe and Cr ions is determined from 2p X-ray photoelectron spectra and Mössbauer spectra. XPS are assigned based on calculations with allowance for the multiplet splitting, crystal field, and the charge-transfer effects. Cobalt ions are found to be bivalent in tetrahedral coordination; chromium ions are trivalent in octahedral coordination. Fe ions are mostly in trivalent states, although Fe 2+ ions are also present in significant amounts. Fe 2+ ions are in tetrahedral coordination while Fe 3+ ions occupy both tetrahedral and octahedral sites. Bulk and near-surface elemental compositions of the ceramic grains are noticeably different. Relative Fe 3+ /Fe 2+ contents are the same in the volume and at the surface of the samples; relative number of Fe 3+ ions increases upon the increase of x . A model of partly inverse spinel structure is suggested where the atoms of iron substitute both Co and Cr atoms. [ABSTRACT FROM AUTHOR]

Ni 1− x Co x Cr 2 O 4 solid solution samples with х = 0, 0.005, 0.01, 0.02, 0.3, 0.5, 0.8 and 1 are studied by the methods of X-ray diffraction and X-ray photoelectron spectroscopy (XPS). Ni2p 3/2,1/2 , Co2p 3/2,1/2 , Cr2p 3/2,1/2 , and O1s spectra are measured. The spectra are calculated with allowance for multiplet splitting, crystal field, and charge-transfer effect. Ni 2+ ions are found to be present in tetrahedral and octahedral positions. Relative numbers of Ni 2+ ions in tetrahedral and octahedral sites are determined via fitting the experimental spectra with superposition of the spectra of Ni 2+ ions calculated in tetrahedral and octahedral crystal field. Cobalt ions are bivalent and occupy mostly tetrahedral sites. Chromium ions are trivalent and occupy predominantly octahedral positions. However, due to a defective lattice, the samples may contain Cr ions in non-equivalent states, either chemically or structurally. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ceramic samples Bi1−x Sr x FeO3±y are synthesized with solid state reaction method. [•] Structures of the samples are studied with XRD. [•] Actual elemental compositions of the samples are considerably different from nominal ones. [•] Chemical bonding and valence state of the Fe ions are studied using Fe2p-, Sr3d-, Bi4f-, O1s-XPS, and Mössbauer spectra. [•] Relative Fe3+/Fe4+ contents are determined from Fe2p-cpectra. [•] Concentration of Fe4+ correlates with that of Sr. [ABSTRACT FROM AUTHOR]

Abstract: Single crystals of La1−x Bi x Mn α O3±β and La1−x−y Bi x A y Mn α O3±β (A=Ba, Pb) are grown, their crystal and electron structure is studied. Relative Mn3+/Mn4+ abundance in each single crystal is determined via fitting experimental Mn2p-spectra with weighted superposition of theoretical spectra of tri- and quadrivalent Mn, and, for barium-free samples, from energy splitting of the Mn3s-spectra components. Strong heterogeneousness of the crystals both in elemental composition and crystal structure is discovered. It is shown that the heterogeneousness displays itself in various oxygenic environments around Mn atoms which give rise to the appearance of Mn4+ ions. A simple model is proposed that allows understanding the nature of the appearance of Mn4+ ions in single crystals of lanthanum–bismuth manganites. [Copyright &y& Elsevier]

Abstract: Ni3s, Ni3p and Ni2p X-ray photoelectron spectra of mono- and binuclear carboxylate complexes of nickel with various geometry of metal atoms environment are obtained. The spectra are calculated in an isolated ion approximation. The dependence of the spectral profiles and the structure of the charge-transfer satellites on the structure of the immediate environment of nickel atoms is established. The data obtained support the results of X-ray diffraction and magnetic studies. [Copyright &y& Elsevier]