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[EN] The BaZrCeYO-BaPrO perovskite system, of interest for high-temperature electrochemical applications involving mixed protonic-electronic conductivity, forms a solid-solution with a wide interval of Ba substoichiometry in the range Ba(CeZr)PrYO, 0 ≤ x ≤ 1. Structural phase transitions mapped as a function of temperature and composition by high-resolution neutron powder diffraction and synchrotron X-ray diffraction reveal higher symmetry for lower Pr content and higher temperatures, with the largest stability field observed for rhombohedral symmetry (space group, R3c). Rietveld refinement, supported by magnetic-susceptibility measurements, indicates that partitioning of the B-site cations over the A and B perovskite sites compensates Ba substoichiometry in preference to A-site vacancy formation and that multiple cations are distributed over both sites. Electron-hole transport dominates electrical conductivity in both wet and dry oxidizing conditions, with total conductivity reaching a value of 0.5 S cm for the x = 1 end-member in dry air at 1173 K. Higher electrical conductivity and the displacement of oxygen loss to higher temperatures with increasing Pr content both reflect the role of Pr in promoting hole formation at the expense of oxygen vacancies. In more reducing conditions (N) and at low Pr contents, conductivity is higher in humidified atmospheres (0.023 atm pHO) indicating a protonic contribution to transport, whereas the greater electron-hole conductivity with increasing Pr content results in lower conductivity in humidified N due to the creation of protonic defects and the consumption of holes., We thank the MINECO, Spain (ENE2015-66183-R and MAT2016-78362-C4-1-R), CSIC, Spain (i-link0743), and CAPES, Brazil (PVE, Proceso 88881.03418/2013-1). Access to the neutron facilities at the Institut Laue Langevin (Grenoble, France) and the National Synchrotron Light Laboratory (LNLS, Campinas, Brazil) under grant 5-24-55(D2B) and research proposal D10B-XRD1-16166, respectively, is gratefully acknowledged. We also thank the FCT, PTDC/CTM-EME/6319/2014, QREN, FEDER, and COMPETE Portugal and the European Social Fund, European Union. U.A. acknowledges the Universidad San Pablo for financial support. We would also like to thank Steven Kermorvant and Alexandre Bosser of the IUT, University of Rennes (France), for assistance.

A complete solid solution forms between the perovskite proton conductor BaZr0.7Ce0.2Y0.1O3-δ (BZCY72) and BaPr0.9Y0.1O3-δ (BPY) on synthesis by the Pechini method and high-temperature annealing. Phase fields of selected members of the Ba(Zr0.7Ce0.2)1-(x/0.9)PrxY0.1O3-δ series were studied as a function of composition and temperature by high-resolution neutron powder diffraction revealing symmetry changes in the sequence Pnma → Imma → → Pm3m. Higher symmetry is favoured for low Pr contents and high temperatures, as consideration of tolerance factor suggests. A volume contraction, ascribed to dehydration, is observed by synchrotron X-ray diffraction on heating in air for lower x. Magnetic measurements and structural data support the presence of Pr in the IV valence state on the perovskite B site. Thermogravimetric analysis in CO2 to ∼1253 K indicates better chemical stability for x ≤ 0.445, whereas decomposition occurred for higher x. Electrical conductivity increases by over two orders of magnitude in dry air at lower temperature from x = 0.225 to 0.675; total conductivity reaches a value of 0.4 S cm-1 at 1173 K for x = 0.675. The series exhibits electron-hole transport with a positive pO2 dependence which increases with temperature, consistent with participation of oxygen vacancies in charge compensation of the Y3+ acceptor dopant. The activation energy for thermally activated hole hopping in air in the range 523-773 K decreases from ∼1 eV for BZCY72 to ∼0.4 eV for x = 0.675. Conductivity is generally lower in humidified N2 and air (pH2O ≈ 0.023 atm) than the corresponding dry atmospheres, consistent with consumption of holes by less mobile protonic species; however for x ≤ 0.225 the lower concentration of electron holes concomitant with higher oxygen-vacancy content in N2 results in slightly higher conductivity in wet conditions due to hydration of vacancies. Fil: Heras Juaristi, Gemma. Instituto de Cerámica y Vidrio de Madrid; España Fil: Amador, Ulises. Universidad San Pablo Ceu; España Fil: Fuentes, Rodolfo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica; Argentina Fil: Chinelatto, Adilson L.. Universidade Estadual de Ponta Grossa; Brasil Fil: Romero De Paz, Julio. Universidad Complutense de Madrid; España Fil: Ritter, Clemens. Institut Laue Langevin; Francia Fil: Fagg, Duncan P.. Universidade de Aveiro; Portugal Fil: Pérez Coll, Domingo. Instituto de Cerámica y Vidrio de Madrid; España Fil: Mather, Glenn C.. Instituto de Cerámica y Vidrio de Madrid; España

The BaZr

We report the rich magnetic behaviour of Sr2CoNb1-xTixO6 (0 ≤ x ≤ 0.5) oxides as a result of their complex microstructure. Although these oxides show an average simple-cubic perovskite structure, they present a flexible microstructure due to short-range ordering between Co/Ti and Nb cations in the perovskite B-sites. The microstructure consists of double-cubic perovskite domains grown in a simple-cubic perovskite matrix. The size and number of the double-cubic perovskite domains decrease as the Ti content increases. As a result of aliovalent substitution of Nb(5+) by Ti(4+) in the parent Sr2CoNbO6 mixed-valence Co(3+)/Co(4+) oxides are obtained. A spin glass-like state has been observed at low temperatures for all the series, with freezing temperatures increasing with the Ti-content in the range 22 to 33 K. Furthermore, the x = 0.3 and x = 0.5 samples show non-interacting superparamagnetic particle-like dynamics associated with relatively high amounts of Co(4+), with "blocking temperatures" of 13 and ∼16 K, respectively. The complex magnetic behaviour of the title oxides seems to be connected with the clustering of magnetic Co(3+) and the distribution of Co(4+) as a result of the microstructure.

The preparation of materials with structures composed of multiple metal cations that occupy specific sites is challenging owing to the difficulty of simultaneously addressing the incorporation of different elements at desired precise positions. We report how it is possible to use a metal-organic framework (MOF) built with a rod-shaped inorganic secondary building unit (SBU) to combine multiple metal elements at specific positions in a manner that is controllable at atomic and mesoscopic scales. Through the combination of four different metal elements at judiciously selected molar ratios, 20 MOFs of different compositions and the same topology have been prepared and characterized. The use of diffraction techniques, supported by density functional theory calculations, has led us to determine various possible atomic arrangements of the metal cations within the SBUs. In addition, seven of the compounds combine multiple types of atomic arrangements, which are mesoscopically distributed along the crystals. Given the large diversity and importance of rod-based MOFs, we believe that these findings offer a new general strategy to produce complex materials with required compositions and controllable arrangements of the metal cations for desired applications., Work at Instituto de Ciencia de Materiales de Madrid–Consejo Superior de Investigaciones Científicas (CSIC) has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO) Projects MAT2013-45460-R, CTQ2014-61748-EXP, and MAT2016-78465-R. F.G. acknowledges financial support from Fundación General CSIC (Programa ComFuturo) and MINECO (Ramón y Cajal program). Computational time has been provided by the Centre de Supercomputació de Catalunya. This work, developed under the HyMAP project, has received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program (grant 648319)., We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).

Single phase, electrically insulating samples of Bi1−xLaxFeO3 solid solutions have been prepared by mechanosynthesis over the whole compositional range for the first time. Lanthanum substitution influenced the kinetics of the mechanochemical reaction and crystallite size of the products. For 0 ≤ x ≤ 0.15, an increase in the La content produced a significant decrease in the weight-normalized cumulative kinetic energy required to obtain the final product and an increase in the resulting crystallite size. Larger La contents did not affect either the reactivity or the crystallite size. The effect of x on the structure has been identified. Samples in the ranges x ≤ 0.15 and x ≥ 0.45 gave single phase solid solutions with R3c and Pnma space groups, respectively, while for the intermediate range, a non-centrosymetric Pn21a(00γ)s00 super structure was obtained. For 0 ≤ x ≤ 0.30, differential scanning calorimetry showed two endothermic effects corresponding to the Neel temperature (TN, antiferromagnetic–paramagnetic transition) and the Curie temperature (TC, ferroelectric–paraelectric transition), demonstrating their multiferroic character. Compositions with a larger La content only showed TN. Dilatometric and permittivity measurements confirmed the results obtained by DSC for the ferroelectric–paraelectric transition. The composition dependence of TN and TC showed that, at low x, TN < TC, but a cross-over, or isoferroic transition occurred at x ∼0.28, when TN = TC = 386 °C. Ceramics with 0 ≤ x ≤ 0.15 were highly insulating at room temperature with a resistivity, extrapolated from the Arrhenius plots, of ∼7 × 1016 to 8 × 1014 Ω cm and an activation energy ∼1.14–1.20 eV. Magnetization of the samples improved with La substitution.

The new scheelite form of SmCrO4 oxide was obtained by heating the zircon-type SmCrO4 oxide at 4 GPa and 803 K. X-ray diffraction revealed that this scheelite SmCrO4 phase crystallized with tetragonal symmetry, S.G. I41/a and lattice parameters: a=0.50776(3) nm and c=1.15606(2) nm. This structural phase transition from zircon to scheelite involved a decreasing of around 10% in the unit cell volume. Although the Cr-O and Sm-O distances did not change very much in both zircon and scheelite polymorphs, the changes occurred in the bond angles were remarkable that appear to support the proposed reconstructive model to explain this structural zircon-scheelite phase transition. Magnetic susceptibility and magnetization measurements revealed that the scheelite SmCrO4 oxide behaved an antiferromagnetic material, where the Sm3+ and Cr5+ were simultaneously ordered. The estimated Neel temperature, TN, was 16 K and the critical field at 12 K associated with the metamagnetic transition was 3.2 T.

The use of nitrite sodalite as a precursor to prepare new blue ultramarine analogs has been investigated. The encapsulation of the chromophores inside of beta cages was achieved by heating the nitrite sodalite precursor with a mixture of sodium carbonate, sulfur, and a reducing agent at about 1000 K under airtight conditions. The obtained new blue ultramarine-type material was characterized by means of X-ray and neutron powder diffraction, transmission electron microscopy, 29Si magic-angle-spinning NMR, IR, Raman, and diffuse reflectance spectroscopies. Thermogravimetric analysis and magnetic measurements were performed in order to determine water and chromophore contents, respectively. On the basis of the spectroscopic results and Rietveld analysis of neutron powder data, the beta cage filling was found to be yellow S2(-) and blue S3(-) chromophores along with carbonate anions. The determined chromophore concentration, about 0.31 mol per formula unit, is enough to have greenish-blue ultramarines, which proves that ultramarine analogs can be obtained from nitrite sodalite.

Blue ultramarine pigments with composition Na 7.7 [(Al,Si) 12 O 24 ] · (SO 4 ) 0.9 (S 3 ) 0.8 and Na 6.5 K 0.5 [(Al,Si) 12 O 24 ] · (SO 4 ) 0.9 (S 3 ) 0.7 were synthesized in order to get a deep knowledge of its structure and microstructure. These pigments were prepared following the current industrial method synthesis, which consists of the calcination of the metakaolin, sulphur, sodium carbonate and charcoal under controlled atmosphere. The structural characterization of the obtained pigments was performed in detail by the complementary use of different techniques such as X-ray powder diffraction and transmission electron microscopy (SAED and HRTEM) together with 29 Si MAS-NMR and IR spectroscopies. The obtained results have allowed to propose a structural model with the lowest symmetry for ultramarine pigments. The suitable space group to describe this structure is P 23 (No.195), which takes account the observed β-cage cluster ordering at the unit cell level and the framework adaptation to the different size of the β-cage clusters.

Strontium cerate (SrCeO(3)) is the parent phase of a family of prototype proton-conducting perovskites with important potential applications as electrolytes in protonic ceramic fuel cells, hydrogen-separation membranes, and sensors for hydrogen and humidity. Apparent nonstoichiometric behavior and the microstructure of SrCeO(3) have been investigated. Phase analysis by X-ray diffraction indicates that single-phase material in the system Sr(1+x)CeO(3+)delta is obtained for compositions x = 0.02-0.03 and that nominally stoichiometric SrCeO(3) (x = 0) synthesized by either solid-state reaction or the citrate method is Sr-rich. Selected area electron diffraction confirms that the system crystallizes with the GdFeO(3)-type orthorhombic perovskite structure (space group Pnma). Structural defects characterized by high-resolution transmission electron microscopy include twin domain boundaries and SrO-rich, Ruddlesden-Popper-type planar defects. Magnetic susceptibility measurements down to 2 K indicate that the Ce(3+) content is minor ( approximately 0.01 mol per formula unit for slow-cooled material) and does not influence the observed nonstoichiometry.

This paper reports the specific conditions used in the preparation of the dimorphic phases of HoCrO4 oxide. The scheelite form has been obtained from the room pressure stable HoCrO4–zircon heated at 823 K at 40 kbar. The structures of both the polytypes have been refined from X-ray powder diffraction data using the Rietveld method. The zircon type of HoCrO4 oxide crystallizes with tetragonal symmetry, S.G. I41/amd and lattice parameters a = 7.119(10) and c = 6.2557(5) A; while the scheelite–HoCrO4 derivative shows tetragonal symmetry, S.G. I41/a and lattice parameters a = 5.0017(1) and c = 11.2664(2) A. Magnetic susceptibility measurements show that both zircon and scheelite forms of HoCrO4 oxide present a very different magnetic behaviour at low temperatures. The zircon form behaves as a ferromagnet with a Curie temperature of 17.6 K, while the scheelite form is antiferromagnetic with a Neel temperature of 7.6 K. A metamagnetic transition for the scheelite form with a critical field of 1 T at 2 K has been also observed. The changes in the sign of the interactions have been also analyzed by considering the possible super-exchange mechanisms and the differences found in the Ho–O–Cr distances and bond angles in going from zircon to scheelite structural type.

Five novel metal organic frameworks were obtained by hydro-solvothermal reactions using the hexafluorisopropylidenebis(benzoic) acid (H2hfipbb) as linker and Co(II) or Mn(II) ions as connectors. [Co2(Hhfipbb)(TEA)], compound 1 (TEA = triethanolamine trianion) with a three-dimensional (3D) framework, and a tpu net; [Co1.5(hfipbb)2]·HN(CH2CH3)3 and [Co3(hfipbb)2]·2{HN(CH2CH3)3}, compounds 2 and 2-a, respectively, both with two-dimensional structure, sql topologies, and different layer packings. Compounds 3 and 4, having the general formula [M2(hfipbb)2]·C7H8, where M = Co (3) or Mn (4), have 3D frameworks with an sqc topology. A deep analysis of the magnetic measurements reveals different striking magnetic behaviors resulting from diverse secondary building unit and framework architectures. Compound 1 presents canted antiferromagnetic chains, compound 2 contains ferromagnetic linear trimeric clusters, and compound 3 exhibits ferromagnetic chains. For the three compounds, a 3D canted antiferromagnetic structure takes place at ∼8 K by means of weak magnetic interactions between the mentioned magnetic units. Such long-range magnetic order is precluded with the application of a high enough magnetic field. Compound 4 evidenced intrachain antiferromagnetic interactions., This work has been supported by the Spanish MCYT Project No. MAT2010–17571 MAT2013–45460, FAMA S2009/MAT-1756 Comunidad Autónoma de Madrid, and Consolider-Ingenio CSD2006–2001.

The new oxide Ba 2 ScCoO 5 has been synthesised by solid state reaction and characterised by using both X-ray and electron diffraction techniques. It crystallises in a perovskite-type structure, showing cubic symmetry, space group Pmm [a=4.1400(9) A]. χ dc and χ ac magnetic susceptibility have been measured down to 1.6 K and analysed, indicating the existence of a freezing phenomenon corresponding to a spin glass state. In the high temperature range, χ dc shows a Curie-Weiss like behaviour, with magnetic correlations starting around T C =50 K. Below this temperature, a strong irreversibility in χ vs. T curves obtained by zero field cooled and field cooled processes (ZFC/FC) has been detected. A second magnetic transition to a spin-glass phase is observed at T F =35 K in the ZFC curve. χ ac measurements performed at different frequencies and magnetic fields also show all the common features characteristic of re-entrant spin-glasses. A possible origin of this magnetic behaviour is proposed and discussed.

A promising group of inorganic salts recently emerged for the negative electrode of advanced lithium-ion batteries. Manganese carbonate combines low weight and significant lithium storage properties. Electron paramagnetic resonance (EPR) and magnetic measurements are used to study the environment of manganese ions during cycling in lithium test cells. To observe reversible lithium storage into manganese carbonate, preparation by a reverse micelles method is used. The resulting nanostructuration favors a capacitive lithium storage mechanism in manganese carbonate with good rate performance. Partial substitution of cobalt by manganese improves cycling efficiency at high rates.

Five novel metal organic frameworks, belonging to three structural types, have been obtained hydrothermally. Three of them, with formula [M3(hfipbb)2(OH)2(H2O)] (M = Mn, Co, Ni; hfipbb = 4,4′-(hexafluoroisopropylidene)bis(benzoate) dianion) belong to the first structural type. The crystal structure of the Mn-based compound was obtained from single crystal synchrotron X-ray diffraction data, while the isostructural compounds of Co and Ni were studied by means of Rietveld analysis using powder X-ray diffraction data. The magnetic behavior of the compounds with M = Co and Ni is characterized by the onset of long-range ferromagnetic order at very low temperature with Curie temperatures near 8 and 2.5 K, respectively. Such spontaneous magnetization seems to be preceded by low-dimensional magnetic interactions, due to the nature of the secondary building units (SBUs) of the structure, which are triple chains built by M3O14 units. Structural and topological analyses of [Mn2(hfipbb)2(H2hfipbb)] and [Co2(hfipbb)2(H2hfipbb)] (2 and 3 structural types, respectively; H2hfipbb = 4,4′-(hexafluoroisopropylidene)bis(benzoic acid)) demonstrate that the packing of the rod-shaped SBUs in 2 prevents the framework interpenetration giving rise to a bnn net whereas 3 is a 2-fold interpenetrated pcu net with isolated paddle-wheel clusters as SBUs pcu. Concerning the magnetic behavior of 2 and 3, antiferromagnetic interactions observed at very low temperature (magnetic susceptibility maximum at 2.8 and 18 K, respectively) are confined to the secondary building units. Fil: Bernini, Maria Celeste. Universidad Nacional de San Luis; Argentina. Instituto de Ciencia de Materiales de Madrid; España. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis; Argentina Fil: Platero Prats, Ana E.. Instituto de Ciencia de Materiales de Madrid; España Fil: Snejko, Natalia. Instituto de Ciencia de Materiales de Madrid; España Fil: Gutierrez Puebla, Enrique. Instituto de Ciencia de Materiales de Madrid; España Fil: Labrador, Ana. BM16-LLS European Synchrotron Radiation Facility; Francia Fil: Saez Puche, Regino. Universidad Complutense de Madrid; España Fil: Romero de Paz, Julio. Universidad Complutense de Madrid; España Fil: Monge, M. Angeles. Instituto de Ciencia de Materiales de Madrid; España

In the search for new materials potentially useful as SOFC components perovskite-like oxides of the Sr2EuNb1−xTixO6−δ series have been obtained, the solubility limit being ca. x = 0.15. Rietveld refinements of XRD data and SAED and HRTEM have demonstrated that these compounds are monoclinic with cell parameters a ≈ b = ap√2 ≈ 5.88 A, c = 2ap ≈ 8.28 A, and S.G. P21/n. As required for SOFC materials, these oxides are stable under a wide range of oxygen partial pressures from the ambient condition to pO2 ≈ 10−30 atm. Aliovalent substitution of Nb5+ by Ti4+ improves the electrical conductivity in air by two orders of magnitude for the end-member of the series (x = 0.15) compared with the parent material. Magnetic measurements, pO2 dependence of conductivity and ion-blocking measurements demonstrate that the predominant conduction mechanism depends on the oxygen partial pressure. In the high pO2 region (from 10−5 to 0.21 atm) p-type conduction is dominant due to the presence of oxygen vacancies which are being annihilated as pO2 increases. Under severe reducing conditions (pO2 below 10−22 atm), n-type conduction dominates. Magnetic measurements demonstrate reduction of Eu3+ occurs whereas the rest of the elements remain in their highest oxidation states. Thus, the Eu3+/Eu2+ redox pair participates in the equilibrium defect responsible for n-type conduction. For intermediate pO2 (10−20 to 10−8 atm) a significant pO2-independent ionic conduction, due to the motion of anionic vacancies, is the dominant conduction mechanism, though a minor electronic n-type contribution is also observed, associated with the reduction of Eu3+ (this occurs at pO2 as high as 10−10 atm). Oxides in the Sr2EuNb1−xTixO6−x/2 series constitute an interesting example of rare-earth perovskites in which the rare-earth ions play a role not only in the structural but also in the electrical behaviour.

Substitution of La(3+) by Sr(2+) in the double perovskite La(2)CoTiO(6) yields materials of the La(2-x)Sr(x)CoTiO(6) series showing a significant amount of trivalent cobalt ions when prepared at ambient atmosphere. The as-prepared compounds can be reduced in severe conditions retaining the perovskite structure while inducing the formation of a large amount of oxygen vacancies. The limit of aliovalent substitution in this series was found to extend up to x = 1. For substitution of La(3+) up to 15% cobalt and titanium are ordered, though the order is progressively lost as x increases; for x≥ 0.30 no ordering is observed as evidenced by magnetic measurements. The ability of these materials to present either cobalt ions in a mixed oxidation state or large amounts of anion vacancies depending on the atmosphere makes them interesting to be further investigated regarding their electrical and electrochemical properties, and hence, their usefulness in some electrochemical devices.