Development of Nanostructured Lanthanum Strontium Cobalt Ferrite/Gadolinian-Doped Ceria Composite Electrodes of Solid Oxide Cells Formed by In Situ Polarization.

In the development of nanoscale oxygen electrodes of high-temperature solid oxide cells (SOCs), the interface formed between the nanoelectrode particles and the electrolyte or electrolyte scaffolds is the most critical. In this work, a new synthesis technique for the fabrication of nanostructured electrodes via in situ electrochemical polarization treatment is reported. The lanthanum strontium cobalt ferrite (LSCF) precursor solution is infiltrated into a gadolinia-doped ceria (GDC) scaffold presintered on a yttria-stabilized zirconia (YSZ) electrolyte, followed by in situ polarization current treatment at SOC operation temperatures.

Enhanced Oxide Ion Conductivity by Ta Doping of BaNbTaMoO.

Significant oxide ion conductivity has previously been reported for the BaM'M″O family (M' = Nb, V; M″ = Mo, W) of cation-deficient hexagonal perovskite derivatives. These systems exhibit considerable structural disorder and competitive occupation of two distinct oxygen positions (O3 site and O2 site), enabling two-dimensional (2D) ionic conductivity within the plane of the structure; higher occupation of the tetrahedral O3 site vs the octahedral O2 site is known to be a major factor that promotes oxide ion conductivity. Previous chemical doping studies have shown that substitution of small amounts of the M' or M″ ions can result in significant changes to both the structure and ionic conductivity.

Proton and Oxide Ion Conductivity in Palmierite Oxides.

Solid proton and oxide ion conductors have key applications in several hydrogen-based and energy-related technologies. Here, we report on the discovery of significant proton and oxide ion conductivity in palmierite oxides AVO (A = Sr, Ba), which crystallize with a framework of isolated tetrahedral VO units. We show that these systems present prevalent ionic conduction, with a large protonic component under humidified air ( ∼ 0.

Magnetic Phase Separation in the Oxypnictide SrCrMnAsO.

Layered SrMAsO-type oxypnictides are composed of tetrahedral MPn and square planar MO layers, the building blocks of iron-based and cuprate superconductors. To further expand our understanding of the chemical and magnetic properties of the SrCrMnAsO solid solution, SrCrMnAsO has been synthesized. The compound crystallizes in the 4/ tetragonal space group with a refined stoichiometry of SrCrMnAsO.

Localized Spin Dimers and Structural Distortions in the Hexagonal Perovskite BaCaMoO.

Extended solid-state materials based on the hexagonal perovskite framework are typified by close competition between localized magnetic interactions and quasi-molecular electronic states. Here, we report the structural and magnetic properties of the new six-layer hexagonal perovskite BaCaMoO. Neutron diffraction experiments, combined with magnetic susceptibility measurements, show that the MoO dimers retain localized character down to 5 K and adopt nonmagnetic spin-singlet ground states.

Variable Temperature Neutron Diffraction Study of the Oxide Ion Conductor BaVWO.

BaVWO is an oxide ion conductor with a bulk conductivity of 5.0 × 10 S cm at 600 °C. BaVWO is anomalous to the other BaM'M″O (M' = Nb; M″ = Mo, W) oxide ionic conductors, as it exhibits cation order with vanadium and tungsten on the M1 site only.

Investigation of the Crystal Structure and Ionic Pathways of the Hexagonal Perovskite Derivative BaVMoO.

The hexagonal perovskite derivatives BaNbMoO, BaNbWO, and BaVWO have recently been reported to exhibit significant oxide ion conductivity. Here, we report the synthesis and crystal structure of the hexagonal perovskite derivative BaVMoO. Rietveld refinement from neutron and X-ray diffraction data show that the cation vacancies are ordered on the M2 site, leading to a structure consisting of palmierite-like layers of M1O polyhedra separated by vacant octahedral layers.

Electronic and Magnetic Properties of Cation Ordered SrMnCrAsO.

Several different mechanisms of magnetoresistance (MR) have been observed in 1111 LnMnAsOF oxypnictides (Ln = lanthanide) as a result of magnetic coupling between the Mn and Ln. Such phases also exhibit interesting magnetic phase transitions upon cooling. SrMnCrAsO has been synthesized to investigate if it is possible to observe MR and/or magnetic phase transitions as a result of magnetic coupling between the Mn and Cr.

High oxide ion and proton conductivity in a disordered hexagonal perovskite.

Oxide ion and proton conductors, which exhibit high conductivity at intermediate temperature, are necessary to improve the performance of ceramic fuel cells. The crystal structure plays a pivotal role in defining the ionic conduction properties, and the discovery of new materials is a challenging research focus. Here, we show that the undoped hexagonal perovskite BaNbMoO supports pure ionic conduction with high proton and oxide ion conductivity at 510 °C (the bulk conductivity is 4.

Hexagonal perovskite derivatives: a new direction in the design of oxide ion conducting materials.

Various structural families have been reported to support oxide ion conductivity; among these, perovskite conductors have received particular attention. The perovskite structure is generally composed of a framework of corner-sharing octahedral units. When the octahedral units share their faces, hexagonal perovskites are formed.

Physicochemical Tools: Toward a Detailed Understanding of the Architecture of Targeted Radiotherapy Nanoparticles.

Targeted radiotherapy is proving to be an effective alternative to external beam radiotherapy for cancer treatment. Gold nanoparticles are biocompatible, commercially available, and readily functionalized, which makes them perfect candidates for the delivery of cytotoxic radionuclides labeled with antibodies to proteins abnormally expressed on cancer tissue. However, there is a lack of information regarding the efficacy of the successive modification steps involved in the functionalization process, as well as of the actual final state of the nanoparticles prior to preclinical tests, which results in a very inefficient screening and that will further impact on biological barriers, such as half-life interactions with serum proteins.

Relationship between the Crystal Structure and Electrical Properties of Oxide Ion Conducting BaWNbO.

The oxide ionic conductor BaWNbO has been synthesized as part of an investigation into the new class of BaM'M''O (M' = W, Mo; M'' = Nb) oxide-ion conducting hexagonal perovskite derivatives. The substitution of W for Nb in BaWNbO leads to an increase in the oxygen content, which enhances the low-temperature ionic conductivity. However, at 400 °C, the ionic conductivity of BaWNbO is still significantly lower than the molybdenum compound BaMoNbO.

Electrical and Structural Characterization of BaMoNbO: The Relationship between Mixed Coordination, Polyhedral Distortion and the Ionic Conductivity of BaMoNbO.

The electrical and structural properties of the series BaMoNbO (x = 0.0, 0.1, 0.

The Crystal Structure of BaNbO Revisited: A Neutron Diffraction and Solid-State NMR Study.

The structure of BaNbO has been investigated using high resolution neutron powder diffraction. Our results show that, while the structure has some features in common with the 9R perovskite and palmierite structures, it is a new and distinct structure. It is shown to follow a (chh)(hhc)(chh) sequence with BaO packing layers and is a cation- and anion-deficient 9H perovskite polytype.

Oxide Ion Conductivity in the Hexagonal Perovskite Derivative BaMoNbO.

Oxide ion conductors are important materials with a range of technological applications and are currently used as electrolytes for solid oxide fuel cells and solid oxide electrolyzer cells. Here we report the crystal structure and electrical properties of the hexagonal perovskite derivative BaMoNbO. BaMoNbO crystallizes in a hybrid of the 9R hexagonal perovskite and palmierite structures.

Absence of colossal magnetoresistance in the oxypnictide PrMnAsO0.95F0.05.

We have recently reported a new mechanism of colossal magnetoresistance (CMR) in electron doped manganese oxypnictides NdMnAsO1-xFx. Magnetoresistances of up to -95% at 3 K have been observed. Here we show that upon replacing Nd for Pr, the CMR is surprisingly no longer present.

A variable temperature synchrotron X-ray diffraction study of the ferroelastic double perovskite Ba2GdMoO6.

A study of the magnetic and structural properties of the double perovskite Ba2GdMoO6 has been performed. The crystal structure distorts from the ideal cubic (Fm3m) structure to the tetragonal space group I4/m at 220 K, before undergoing a second distortion to a triclinic system (I1) at 80 K. The phase transition to triclinic symmetry is also evident in magnetic susceptibility measurements.

Colossal magnetoresistance in Mn2+ oxypnictides NdMnAsO(1-x)F(x).

Colossal magnetoresistance is a rare phenomenon in which the electronic resistivity of a material can be decreased by orders of magnitude upon application of a magnetic field. Such an effect could be the basis of the next generation of memory devices. Here we report CMR in the antiferromagnetic oxypnictide NdMnAsO(1-x)F(x) as a result of competition between an antiferromagnetic insulating phase and a paramagnetic semiconductor upon application of a magnetic field.

Synthesis and characterisation of biologically compatible TiO2 nanoparticles.

We describe for the first time the synthesis of biocompatible TiO2 nanoparticles containing a functional NH2 group which are easily dispersible in water. The synthesis of water dispersible TiO2 nanoparticles coated with mercaptosuccinic acid is also reported. We show that it is possible to exchange the stearic acid from pre-synthesised fatty acid-coated anatase 5-nm nanoparticles with a range of organic ligands with no change in the size or morphology.

Giant magnetoresistance in oxypnictides (La,Nd)OMnAs.

A sizeable negative magnetoresistance (MR) has been observed for oxypnictides LnOMnAs (Ln = La,Nd). MR up to -24% is observed at 200 K for LaOMnAs which is unprecedented for divalent Mn(2+). Both materials are weak ferromagnets with transition temperatures above room temperature.

AM-6: a microporous one-dimensional ferromagnet.

The vanadosilicate zeolite AM-6 is shown by a combination of spectroscopic techniques (UV-vis, Raman, XPS, XAS and EPR) to contain linear chains of alternating V=O and V-O bonds. The V(IV) ions in these chains are ferromagnetically coupled, and an excellent fit a to the susceptibility data with a one-dimensional Heisenberg model is obtained with J = 0.66(1) cm(-1).

Chemical tuning of positive and negative magnetoresistances, and superconductivity in 1222-type ruthenocuprates.

A remarkable variety of conducting states has been found in RuSr2(R2-xCex)Cu2O10-delta ruthenocuprates by tuning the properties of the magnetic CuO2 and RuO2 layers through small changes in the chemistry of the (R,Ce)2O2-delta slab. Both the R3+ cation size and the charge transfer determined by the R/Ce ratio and the oxygen deficiency delta are important controlling parameters that tune ground-state properties from positive magnetoresistive to negative magnetoresistive to superconducting.

A cyclic hexacopper(II) fluoro complex that encapsulates two fluoride anions.

The complex [[Cu3(HpztBu)4(mu-pztBu)2(mu-F)2(mu 3-F)]2]F2 (HpztBu = 3[5]-tert-butylpyrazole) has a cyclic, C2v-symmetric hexacopper core. The two non-coordinated F- anions are encapsulated within cavities formed by three HpztBu ligands.