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In the course of an investigation to prepare the hypothetic new double perovskite La3Co2VO9 with Co2+ and V5+ in octahedral sites, we obtained the new simple perovskite LaCo0.71(1)V0.29(1)O2.97(3) as the main phase. The pure compound was then synthesized by the citrate decomposition method. The crystal structure was studied by X-ray (PXRD) and powder neutron diffraction (PND). Physical properties were characterized by X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and thermogravimetric analysis (TGA). Rietveld refinements were performed in the orthorhombic space group Pnma (#62). Refined cell parameters were a = 5.4762(2) Å, b = 7.7609(2) Å and c = 5.5122(1) Å. Magnetization measurements showed that this perovskite is an antiferromagnet with a Neel temperature of 15 K. At high T the magnetization follows the Curie–Weiss law corrected by temperature independent paramagnetism (TIP) showing an effective magnetic moment of 3.03μB well described by the contribution of Co2+ (HS), Co3+ (IS), V3+ and V4+ ions. The crystallographic formula was refined by PND and oxidation state distribution was determined by the combination of PND, XAS, TGA and magnetic measurements. [ABSTRACT FROM AUTHOR]

Abstract: The LHPG technique has been successfully applied to the growth of single crystals in fiber shape with a controlled composition and lattice parameter gradient along the fiber axis. The GdTaO4–ErTaO4 system was chosen for having a full solubility range. The obtained fibers had a constant gradient of lattice parameters along the axis with a value of 1.24%/cm for the (44¯4) reflection, hence of concentration gradient. Structural characterization results showed that the fibers had a good crystalline quality essential for the optimization of others physical properties. Luminescent characterization showed the behavior of the intensity of green and red luminescence (by 488nm pumping) as a function of concentration of Er3+ and three processes populating the levels (2H11/2, 4S3/2) and 4F9/2 by cross-relaxation energy transfer has been proposed. The results presented show that the compositional gradient and the LHPG technique can be used not only for the growth of crystals with controlled lattice parameter gradients, for potential X-ray diffraction applications, but also as a combinatorial method for the rapid study of material properties as a function of concentration using in situ measurements. [Copyright &y& Elsevier]

Abstract: Gradient single crystal fibers of GdTaO4–YbTaO4 have been grown by laser-heated pedestal growth (LHPG). The crystals of the compounds have differences in the lattice parameters of , and . The crystals obtained exhibit an optimum linear distribution of the compounds along the fiber axis and a lattice spacing gradient value of 2.91%/cm for reflection, the largest value of lattice spacing gradient reported up to this moment. The compositional and structural analysis shows that the LHPG technique and the GdTaO4–YbTaO4 system are very promising for obtaining good quality gradient crystals with large lattice parameters gradient. [Copyright &y& Elsevier]

Abstract: The laser heated pedestal growth technique was used to obtain single crystal fiber of M-type GdTaO4. The fibers were around 3cm long, ∅0.8mm, transparent, colorless and did not exhibit any inclusions. The structural quality of the fibers was evaluated by X-ray rocking curve profiles and X-ray topography. Better quality crystals were grown perpendicular to (010) direction presenting rocking curve FWHM typically around 52arcsec for the reflection. The results confirm that good structural fibers can be successfully obtained by the procedure presented here. [Copyright &y& Elsevier]

Abstract: High-resolution Kβ emission spectra of several manganese compounds were measured in order to characterize the dependence of the Kβ′ and Kβ1,3 features, on the chemical environment. High resolution spectra were obtained using a non-conventional spectrometer based on quasi-back-diffraction geometry at National Synchrotron Light Laboratory (LNLS). It was found that the energy of the Kβ′ satellite structure relative to the main Kβ1,3 line decreases linearly with the formal oxidation state for Mn–O systems. A noticeable dispersion of the relative Kβ′ energy for different Mn2+ compounds could be observed. The dependence of the Kβ′ satellite line on the net charge and the effective 3d spin in Mn2+ compounds was investigated. Calculations of the net charge and the effective 3d spin were performed within the density-functional theory using the package SIESTA. A direct relation between this dispersion and the effective Mn 3d spin was found. [Copyright &y& Elsevier]

Highlights: [•] Three new double perovskites BaLaMSbO6 (M=Mn, Co, Ni) were synthesized. [•] Complete structural characterization by Rietveld refinement was performed. [•] Complex magnetic behavior for Mn perovskite was explained by superparamagnetism. [•] Antiferromagnetic behavior at low temperatures is obtained for the three materials. [ABSTRACT FROM AUTHOR]

Abstract: Oxidation state and coordination of transition metal cations seems to be hard to assess when considering multiple cations, each one with different possible oxidation states. In fact, this is the case of the spinel-type double oxides family. High resolution Kβ X-ray fluorescence spectra were measured in Mn(2−x)V(1+x)O4 (x=0 and ) spinels-type double oxides in order to determine the oxidation state and coordination of V and Mn cations. The relative intensity of radiative Auger effect KM2,3M4,5 to the total intensity and the integral absolute difference value were used as reference parameters for the characterization of Mn oxidation states. The coordination of Mn ions was inferred by the intensity of the Kβ5 line. In the case of V compounds, it was used as the intensity of the line Kβ′ relative to the total area of Kβ region. The obtained results were further compared with X-ray absorption spectra analysis, showing good agreements regarding the oxidation state characterization. However, there were found some discrepancies in coordination, due to customary oversimplifications in the Kβ5 line origin. The obtained results might represent valuable and useful data for chemical scopes of characterizing spinel-type oxides family. [Copyright &y& Elsevier]

Abstract: Oxidation states of transition metal cations in spinels-type oxides are sometimes extremely difficult to determine by conventional spectroscopic methods. One of the most complex cases occurs when there are different cations, each one with several possible oxidation states, as in the case of the magnetoresistant Mn(2−x)V(1+x)O4 (x=0, 1/3 and 1) spinel-type family. In this contribution we describe the determination of the oxidation state of manganese and vanadium in Mn(2−x)V(1+x)O4 (x=0, 1/3,1) spinel-type compounds by analyzing XANES and high-resolution Kβ X-ray fluorescence spectra. The ionic models found are Mn2+ 2V4+O4, Mn2+ 5/3V3.5+ 4/3O4 and Mn2+V3+ 2O4. Combination of the present results with previous data provided a reliable cation distribution model. For these spinels, single magnetic electron paramagnetic resonance (EPR) lines are observed at 480K showing the interaction among the different magnetic ions. The analysis of the EPR parameters show that g-values and relative intensities are highly influenced by the concentration and the high-spin state of Mn2+. EPR broadening linewidth is explained in terms of the bottleneck effect, which is due to the presence of the fast relaxing V3+ ion instead of the weak Mn2+ (S state) coupled to the lattice. The EPR results, at high temperature, are well explained assuming the oxidation states of the magnetic ions obtained by the other spectroscopic techniques. [Copyright &y& Elsevier]

In this work, we report the synthesis as well as the structural and magnetic characterization of the three perovskites La 2 MnB'O 6 (B' = Ti, Zr, and Hf). Interestingly, only La 2 MnTiO 6 crystallizes in the monoclinic double perovskite space group P 2 1 / n , with a complete rocksalt order of the B-site cations, whereas La 2 MnZrO 6 and La 2 MnHfO 6 crystallize in the orthorhombic simple perovskite space group Pbnm , with complete disorder in the B site. Moreover, the magnetic susceptibility at low temperatures shows clear antiferromagnetic transitions below 10 K for the three compounds, but only the Ti-based perovskite has long-range magnetic ordering. The latter compound has an antiferromagnetic type-II structure described by the P S -1 magnetic space group, while the other two have a spin-glass behavior below the transition temperature due to both spin disorder and competing superexchange interactions in the systems. This is the first time that two of the three studied compounds were synthesized (B' = Zr and Hf) and the first time that the whole series is described in thorough detail using symmetry-adapted refinements and magnetic crystallography.

Several detailed studies of the external morphology of the ear region in extinct sloths have been published in the past few decades, and this anatomical region has proved extremely helpful in elucidating the phylogenetic relationships among the members of this mammalian clade. Few studies of the inner ear anatomy in these peculiar animals were conducted historically, but these are increasing in number in recent years, in both the extinct and extant representatives, due to wider access to CT-scanning facilities, which allow non-destructive access to internal morphologies. In the present study, we analyze the extinct ground sloth Glossotherium robustum and provide a description of the external features of the ear region and the endocranial side of the petrosal bone, coupled with the first data on the anatomy of the bony labyrinth. Some features observable in the ear region of G. robustum (e.g., the shape and size of the entotympanic bone and the morphology of the posteromedial surface of the petrosal) are highly variable, both intraspecifically and intraindividually. The form of the bony labyrinth of G. robustum is also described, providing the first data from this anatomical region for the family Mylodontidae. The anatomy of the bony labyrinth of the genus Glossotherium is here compared at the level of the superorder Xenarthra, including all available extant and extinct representatives, using geometric morphometric methods. In light of the new data, we discuss the evolution of inner ear anatomy in the xenarthran clade, and most particularly in sloths, considering the influence of phylogeny, allometry, and physiology on the shape of this highly informative region of the skull. These analyses show that the inner ear of Glossotherium more closely resembles that of the extant anteaters, and to a lesser extent those of the giant ground sloth Megatherium and euphractine armadillos, than those of the extant sloths Bradypus and Choloepus, further demonstrating the striking morphological convergence between the two extant sloth genera.

In this work granular activated carbon has been chosen as an absorbent in order to investigate the Cr(VI) reduced by adsorption experiments. Several batch chromium-sorption experiments were carried out using 0.25 g of granular activated carbon in 50 mL aqueous solution containing approximately 70 and 140 mg L(-1) of Cr(VI) and Cr(III), respectively. Cr-Kbeta fluorescence spectra of Cr adsorbed in a carbon matrix and Cr reference materials were measured using a high-resolution Johann-type spectrometer. Based on evidence from the Cr-Kb satellite lines, the Cr(VI) reduction process has actually happened during metal adsorption by the activated carbon., (Copyright 2010 Elsevier Ltd. All rights reserved.)

Aquatic macrophytes Salvinia auriculata, Pistia stratiotes and Eichhornia crassipes were chosen to investigate the Cr(VI) reduced by root-based biosorption in a chromium uptake experiment, using a high-resolution XRF technique. These plants were grown in hydroponics medium supplied with non-toxic Cr concentrations during a 27-day metal uptake experiment. The high-resolution Cr-Kbeta fluorescence spectra for dried root tissues and Cr reference material (100% Cr, Cr(2)O(3), and CrO(3)) were measured using an XRF spectrometer. For all species of aquatic plant treated with Cr(VI), the energy of the Cr-Kbeta(2,5) line was shifted around 8 eV below the same spectral line identified for the Cr(VI) reference, but it was also near to the line identified for the Cr(III) reference. Moreover, there was a lack of the strong Cr-Kbeta'' line assigned to the Cr(VI) reference material within the Cr(VI)-treated plant spectra, suggesting the reduction of Cr(VI) for other less toxic oxidation states of Cr. As all Cr-Kbeta spectra of root tissue species were compared, the peak energies and lineshape patterns of the Cr-Kbeta(2,5) line are coincident for the same aquatic plant species, when they were treated with Cr(III) and Cr(VI). Based on the experimental evidence, the Cr(VI) reduction process has happened during metal biosorption by these plants.