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Chemical Laboratories, Government P. G. College, Betul-460 001 Manuscript received 21 August 1990, revised 3 June 1991, accepted 11 July 1991 Amperometric Titrations of Praseodymium(III) and Neodymium(III) with Pyrocatechin Violet.

6 páginas, 4 figuras.-- PACS number(s): 71.30.+h, 78.70.Dm, 75.30.Wx, 75.25.Dk.-- et al. ; X-ray absorption spectroscopy measurements in Pr0.5Ca0.5CoO3 were performed at the Pr M4,5, Pr L3, and Ca L2,3 absorption edges as a function of temperature below 300 K. Ca spectra show no changes down to 10 K while a noticeable thermally dependent evolution takes place at the Pr edges across the metal-insulator transition. Spectral changes are analyzed by different methods, including multiple scattering simulations, which provide quantitative details on an electron loss at Pr 4f orbitals. We conclude that in the insulating phase a fraction [15(±5)%] of Pr3+ undergoes a further oxidation to adopt a hybridized configuration composed of an admixture of atomiclike 4f1 states (Pr4+) and f-symmetry states on the O 2p valence band (Pr3+L̲ states) indicative of a strong 4f-2p interaction. ; We acknowledge financial support from MICINN (Spanish government) under Projects No. MAT2009-09308 and Nanoselect Project No. CSD2007-00041. We acknowledge ILL (and the CRG-D1B), and HZB for the provision of beam time. The ALICE diffractometer is funded through the BMBF under Contract No. 05KS7PC1. The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under Grant Agreement No. 226716. J.H.M. thanks CSIC for JAEdoc contract. ; Peer reviewed

The influence of medium doses (from 1019 cm–2 to 1020 cm–2) of irradiation with fast electrons and changes in the concentration of praseodymium in the interval 0.0 ≤ z ≤ 0.5 on the excess conductivity of optimally oxygen-doped Y1Ba2Cu3O7-δ single crystals was studied. It is shown that electron irradiation and an increase in the degree of doping with praseodymium leads to a significant expansion of the temperature interval of the existence of excess conductivity, thereby narrowing the region of the linear dependence of r(Т) in the ab-plane. It was established that at doses 0 ≤ D ≤ 6.5´1019 cm–2 the value of the value of the transverse coherence length ξс(0) increases with an increase in D approximately 3 times and more than four times as the praseodymium content in the sample increases to z ≈ 0.42. At the same time, in both cases, the 2D-3D crossover point is shifted by temperature. In contrast to the case of irradiation with small doses (D ≤ 1019 cm–2) and doping with praseodymium up to concentrations z ≤ 0.39, irradiation with medium doses and doping with praseodymium at higher concentrations leads to a non-monotonic dependence of the transverse coherence length xс(0) with characteristic maxima at D ~ (7-8)´1019 cm–2 and z ≈ 0.42, which may be related to the general suppression of superconducting characteristics.

Department of Chemistry, Government Vidarbha Mahavidyalaya, Amravati-440 604 Manuscript received 18 September 1989, revised 10 July 1990, accepted 22 August 1990 Stability Constants of Mixed Ligand Chelates of Lanthanum(III), Praseodymium(III) and Neodymium(III) with NTA, HEDTA, CYDTA and DTPA as Primary Ligands and some Polymethylene Dicarboxylic Acids as Secondary Ligands

[EN] Composites made of different doped cerias and (La0.8Sr0.2)(0.95)MnO3+ were studied as potential solid oxide fuel cell cathodes. Tb, Pr, Gd and Er have been introduced as ceria dopants to enhance the electrocatalytic properties of (La0.8Sr0.2)(0.95)MnO3+ composites fabricated within. Different electrochemical behaviors were observed for the studied composites depending on lanthanide cation nature, i.e., whether they can exhibit different oxidation states or not. Specifically, (La0.8Sr0.2)(0.95)MnO3+/ceria composites with a mixed valence dopants (Tb and Pr) in the CeO2 structure are the best performing and present a limiting step at low frequencies; whereas those with ceria-doping elements withfixed oxidation state (Gd and Er) exhibit the limiting processes at higher frequencies. This fact is related to the higher magnitude of the TPB enlargement in the composite cathode achieved thanks to the promotion of mixed ionic-electronic conductivity in the Pr/Tb-doped ceria phase.The best cathode performance was obtained with (La0.8Sr0.2)(0.95)MnO3+_Ce0.8Pr0.2O2- cathodes with the lowest values for the polarization resistance in the 900-700 degrees C temperature range. ; Funding from Spanish Government (MINECO ENE2014-57651 grant) is kindly acknowledged. ; Navarrete Algaba, L.; Balaguer Ramírez, M.; Vert Belenguer, VB.; Serra Alfaro, JM. (2017). Tailoring Electrocatalytic Properties of Solid Oxide Fuel Cell Composite Cathodes Based on (La0.8Sr0.2)(0.95)MnO3+delta and Doped Cerias Ce(1 x)Ln(x)O(2 delta) (Ln=Gd, La, Er, Pr, Tb and x=0.1 0.2). Fuel Cells. 17(1):100-107. https://doi.org/10.1002/fuce.201600133 ; S ; 100 ; 107 ; 17 ; 1 ; Minh, N. Q. (1993). Ceramic Fuel Cells. Journal of the American Ceramic Society, 76(3), 563-588. doi:10.1111/j.1151-2916.1993.tb03645.x ; Mizusaki, J. (2000). Electronic conductivity, Seebeck coefficient, defect and electronic structure of nonstoichiometric La1â xSrxMnO3. Solid State Ionics, 132(3-4), 167-180. doi:10.1016/s0167-2738(00)00662-7 ; Jiang, S. P. (2003). Issues on development ...

Pr3+-doped Y2O3 nanocrystals (NCs) have been obtained via five wet-chemistry synthesis methods which were optimized in order to achieve superior optical properties. To this end, a systematic study on the influence of different reaction parameters was performed for each procedure. Specifically, precursor concentration, reaction temperature, calcination temperature, and time, among others, were analyzed. The synthesized Y2O3: Pr3+ NCs were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and reflectance and Raman spectroscopy. In addition, the optical properties of such NCs were investigated by excitation, emission, and luminescence decay measurements. Concretely, emission from the 1D2 level was detected in all samples, while emission from 3PJ was absent. Finally, the effect of the synthesis methods and the reaction conditions on the luminescence decay has been discussed, and a comparative study of the different methods using the fluorescence lifetime of so-obtained Y2O3: Pr3+ NCs as a figure of merit has been carried out. ; This work was funded with a Future and Emerging Technologies (FET) NCLas project; European Union; Proposal: 829161.

Rare, valuable and with unpronounceable names like praseodymium, critical minerals are the foundations of the technologies on which much modern life depends. Packed into the circuit boards of our smartphones and tablets are chemical elements ...

The heat capacity and thermal conductivity of multiferroics Bi1–xPrxFeO3 (0 ≤ x ≤ 0.50) has been studied in the temperature range of 130–800 K. A slight substitution of praseodymium for bismuth is found to lead to a noticeable shift of the antiferromagnetic phase transition temperature whilst the heat capacity increases. The temperature dependences of the heat capacity and thermal conductivity exhibit additional anomalies during phase transitions. The experimental results suggest that the excess heat capacity can be attributed to the Schottky effect for three-level states. The basic mechanisms of the heat transfer of phonons are highlighted and the dependence of the mean free path on temperature is determined. ; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART²

The paper presents the experimental results of the rare earth elements and yttrium (REY) biosorption in the natural surface waters and groundwater in the presence of living and inactivated organotrophic bacteria (Curtobacterium sp., Ralstonia sp., Pseudomonas sp., Bacillus sp., Brevibacterium sp., Microbacterium sp.,) under different environmental pH conditions. We find that the biosorption process is mainly regulated by two factors: the aqueous solution's pH and the bacteria strains concertation. The water acidity significantly effects on the bacteria sorption capacity for all studied strains. We discover a decrease in REY sorption with an increase in pH due to lower absorption of REY on the cell walls of bacteria. The process of REY biosorption proceeds more intensively by living bacteria than in the presence of inactivated microorganisms. We observe that at neutral pH values all studied bacterial strains sorb light REY (lanthanum, praseodymium, neodymium), in more acidic solutions (pH 2) the heavy ones (lutetium, europium). The REY sorption decreased with an increase in the living and inactivated bacterial concentration.