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The Pechini sol-gel method was applied to obtain LiMn2-xTxO4 (T = Ni, Fe; x = 0.1 to 0.5) nanopowders. Crystal and electronic structures, chemical composition and magnetic properties of the materials were characterized by X-ray diffraction, XPS, SEM/EDX microscopy, prompt gamma-ray activation analysis (PGAA), Mössbauer spectroscopy and magnetic susceptibility, respectively. XRD measurements showed that the LiMn2-xNixO4 were single phase for x = 0.1 and 0.2. Three samples with higher Ni content contained some addition of a second phase. Analysis of the oxidation state of the dopants by XPS revealed ionic Ni2+ and Fe3+. Mössbauer spectroscopy also confirmed 3+ oxidation state of iron and its location in octahedral sites, which excluded the inverse spinel configuration. XPS examinations showed that Mn3+ ions dominated in the iron substituted series whereas the Mn4+ was dominant in the nickel series. [ABSTRACT FROM AUTHOR]

A new chemical synthesis route by a thermal decomposition of nitrates and acetates, preceded by solution displacement reaction, was successfully applied to obtain the YF 3 :1%RE (RE = Pr, Ho, Er and Tm) and LaF 3 :1%Pr nanocrystals. The samples were characterized by the following methods: X-ray diffraction, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), magnetic susceptibility thermal dependence measurements and electron paramagnetic resonance (EPR). The obtained YF 3 :1%RE (RE = Pr, Ho, Er and Tm) materials crystallized with orthorhombic symmetry, whilst LaF 3 :1%Pr exhibits hexagonal structure. Chemical composition determined by EDX, XPS and magnetic measurements was close to nominal formula. SEM images show the nanometric size of the grains. Surface contamination can be suggested to be responsible for the deterioration of the optical properties of the composites. [ABSTRACT FROM AUTHOR]

Abstract: The X-ray absorption K-edges of sulfur in CuCr2−x Sb x S4 (x =0.3, 0.4, 0.5) have been measured and compared to linearized augmented plain wave (LAPW) numerical calculations. The near edge region is generated by magnetically polarized and hybridized S 2p energy levels and shows small change with increased Sb content, which can be attributed to the movement of Cr 3d spin-down states up on the energy scale. The LAPW result confirms this effect. Moreover, the calculations show that the antimony in those spinels is rather in +3 than in +5 valence state. The calculated magnetic moment on Cr equals to 2.72μ B. In EXAFS, there is no visible change between x =0.3 and 0.5 spectra, which indicates that the local structure does not change significantly. [Copyright &y& Elsevier]

Materials for ultrafast femtosecond lasers, CaGdAlO 4 (CGA) single crystals, undoped and doped nominally with 8% at. of Yb, were grown by the Czochralski method in [100] direction. X-ray analyses showed the ideal disorder on Gd/Ca sites. The decrease of unit cell volume for the crystal doped with Yb was observed. Magnetic measurements revealed that undoped and doped samples were paramagnetic. The real concentration of Yb was determined as 5% at. The XPS lines: O1s, Al2p and Ca2p are complex and they consist of the main line and additional lines at lower and higher binding energy. The intensities of additional lines decrease comparing the end and cone part of crystal, indicating an improvement of crystal structure during the growth process. XPS chemical analyses showed deficiency of Al and Ca and excess of oxygen. The oxygen excess may exist in two contributions: in one, to keep the charge neutrality as Gd-O x sheets between CGA; the second as interstitial oxygen, responsible for brownish coloration of crystals. Dielectric properties are close to values measured for similar compounds CaYAlO 4 , CaNdAlO 4 , and SrLaAlO 4. • The ideal disorder on Gd/Ca sites was confirmed by X-ray measurements. • The XPS O1s, Al2p and Ca2p lines are complex due to defects in crystal structure. • The charge neutrality might be ensured by Gd-O x sheets between CGA. • Defects narrow the energy band gap from 4.6 to 4 eV. [ABSTRACT FROM AUTHOR]

The modified sol-gel method was used to obtain of Y 4 Al 2 O 9 nanopowders co-doped with Tb, Yb cations. SEM microstructure examination proved that nanoscale grains were obtained in all samples. Complex lines of Y3d, O1s and Al2p were found in the photoelectron spectra. The XPS energy gap in the valence band was estimated as about 4.6 eV. Results of SQUID magnetometry measurements confirmed nominal concentration of the co-dopants. [ABSTRACT FROM AUTHOR]

Abstract: The process of sol–gel synthesis was applied to obtain LiMn1.5 M 0.5O4 (M=Al, Mg, Ni, Fe) and LiMn2O4/TiO2 nanopowders. The samples were characterized by following methods: X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), X-ray photoelectron spectroscopy (XPS) and SQUID magnetometry. XPS was used to examine the chemical composition and oxidation state of manganese, in particular the Mn3+/Mn4+ ratio from the deconvolution of the complex Mn3p lines. The size of the grains and crystallites were independently obtained from SEM images and XRD patterns, respectively. In all the cases a critical interplay of electronic (Mn3+/Mn4+ ratio), structural (unit cell volume) and magnetic properties was observed depending on the synthesis process. [Copyright &y& Elsevier]

Highlights: [•] SrLaAlO4: Mn nano and single crystals were examined by XRD method to determine the crystal structure. [•] SEM/EDX imaging has been done. [•] XPS electronic structure was examined and discussed. [•] Experimental effective magnetic moment and the calculated one were compared. [Copyright &y& Elsevier]

Abstract: Sr2CeO4 is a very promising material due to its various industrial applications, e.g. for the construction of field emission displays and light emitting diodes. In this work, the phosphor was synthesized by the sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) methods. They proved to be very good structural properties of the material and identified negligible impurities from the technological process. The decomposition of the surface of the nanocrystals was found but this did not decrease the spectral features of the compound. The analysis of the XPS O2p lines revealed contributions of two kinds of bonds: terminal and equatorial ones, in the ratio of 2/4. They are separated by 1.2eV what is in agreement with the observed absorption spectra. A presence of the decomposed layers may produce asymmetric widening of the emission spectra towards a lower energy. [Copyright &y& Elsevier]

The process of sol-gel synthesis was applied to obtain the LiMn2O4 nanopowders. The samples were characterized by the following methods: scanning electron microscopy (SEM/EDX), X-ray photoelectron spectroscopy (XPS), SQUID magnetometry and electron paramagnetic resonance (EPR). Chemical composition, oxidation state of manganese and magnetic properties were determined. The SEM images showed grains in the form of nanocrystals or larger conglomerates, depending on the synthesis process. From XPS analysis chemical formulas of the examined compounds were determined. Deconvolution of complex Mn3p lines was used to find the ratio of Mn3+/Mn4+. This ratio was observed to depend on the synthesis process. The C1s lines of the measured samples were intense and complex. The results of magnetic measurements and EPR showed the presence of some extra magnetic phases. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]