The Fluorite-Like Phase Nd5Mo3O16±Î´ in the MoO3-Nd2O3 System: Synthesis, Crystal Structure, and Conducting Properties.

This paper describes a study of the system MoO3-Nd2O3 using a combination of X-ray powder diffraction (XRD), neutron powder diffraction (NPD), thermogravimetric analysis (TGA), and ac impedance spectroscopy (IS). A phase-pure material is observed at a composition of 45.5 mol % Nd2O3, which corresponds to an ideal stoichiometry of Nd5Mo3O16.5. XRD and NPD show that the crystal structure is a superstructure of the fluorite arrangement, with long-range ordering of the two cation species leading to a doubled unit cell parameter. The sample is found to be significantly oxygen deficient, i.e. Nd5Mo3O15.63(4), when it is prepared by a solid-state reaction at 1473 K in air. TGA measurements indicate that the sample loses only minimal mass on heating to 1273 K in O2. IS studies of the mean conductivity under different atmospheres show that the sample is a mixed conductor between ambient temperature and 873 K, with a dominant electronic component at higher temperatures, as demonstrated by measurements under inert atmosphere. NPD measurements indicate that the anion vacancies are preferentially located on the O2 sites, while studies of the temperature dependence performed under an O2 atmosphere to 1273 K show significantly anisotropic thermal parameters of the anions. Together with analysis of the total neutron scattering data, this supports a model of oxygen ions hopping between O2 positions, with a vacancy, rather than interstitial, mechanism for the anion diffusion.

Role of the doping level in localized proton motions in acceptor-doped barium zirconate proton conductors.

Acceptor-doped barium zirconates are currently receiving considerable interest because of their high proton conductivity at intermediate temperatures, making them applicable as electrolytes in various electrochemical devices, but the mechanism of proton conduction is unclear. Here, we investigate the role of the acceptor-dopant level in the localized proton motions, i.e. proton transfers between oxygens and O-H reorientations, in hydrated samples of the proton conducting, acceptor-doped, perovskites BaZr1-xInxO3-x/2 with x = 0.10 and 0.20, using quasielastic neutron scattering (QENS). Analysis of the QENS spectra reveals that several proton transfer and O-H reorientational motions contribute to the QENS signal, as a consequence of the locally disordered nature of the structure due to the In doping of these materials, and establishes a generic and complex picture of localized proton dynamics in acceptor-doped barium zirconate based proton conductors. A comparison of the QENS results with vibrational spectroscopy data of the same materials, as reported in the literature, suggests a predominance of O-H reorientational motions in the observed dynamics. The highest doping level corresponds to a more distorted structure and faster dynamics, which thus indicates that some degree of structural disorder is favourable for high local proton mobility.

C-type related order in the defective fluorites La2Ce2O7 and Nd2Ce2O7 studied by neutron scattering and ab initio MD simulations.

This work presents a structural investigation of La2-xNdxCe2O7 (x = 0.0, 0.5, 1.0, 1.5, 2.0) using X-ray powder diffraction and total scattering neutron powder diffraction, analysed using Rietveld and the reverse Monte Carlo method (RMC). Ab initio molecular dynamics (MD) modelling is also performed for further investigations of the local order. The main intensities in the neutron diffraction data for the La2-xNdxCe2O7 series correspond to the fluorite structure. However, additional C-type superlattice peaks are visible for x > 0 and increase in intensity with increasing x. The Nd-containing compositions (x > 0) are best fitted with Rietveld analysis by using a combination of oxygen deficient fluorite and oxygen excess C-type structures. No indications of cation order are found in the RMC or Rietveld analysis, and the absence of cation order is supported by the MD modelling. We argue that the superlattice peaks originate from oxygen vacancy ordering and associated shift in the cation position away from the ideal fluorite site similar to that in the C-type structure, which is seen from the Rietveld refinements and the observed ordering in the MD modelling. The vacancies favour alignments in the 〈110〉, 〈111〉 and especially the 〈210〉 direction. Moreover, we find that such ordering might also be found to a small extent in La2Ce2O7, explaining the discernible modulated background between the fluorite peaks. The observed overlap of the main Bragg peaks between the fluorite and C-type phase supports the co-existence of vacancy ordered and more disordered domains. This is further supported by the observed similarity of the radial distribution functions as modelled with MD. The increase in long range oxygen vacancy order with increasing Nd-content in La2-xNdxCe2O7 corresponds well with the lower oxide ion conductivity in Nd2Ce2O7 compared to La2Ce2O7 reported earlier.

Hydration thermodynamics of the proton conducting oxygen-deficient perovskite series BaTi1-xMxO3-x/2 with M = In or Sc.

This article establishes the effect of structure and composition on water uptake and the hydration and proton transport properties of the oxygen-deficient perovskite series BaTi1-x(In,Sc)xO3-x/2, with 0.2 ≤ x ≤ 0.7. The equilibrium water uptake is determined by thermogravimetry, while combining thermogravimetry with differential scanning calorimetry allows for direct determination of the materials' hydration thermodynamics. Proton and oxide ion transport properties are characterized by means of ac impedance measurements up to 1000 °C. In general, the hydration thermodynamics of the scandates are more favorable than that of the indates and are also affected by changes in crystal structure throughout the series. The more favorable hydration thermodynamics of cubic scandates increase their proton conductivity at higher temperatures compared to their indate counterparts. In contrast to the BaTi1-xInxO3-x/2 series, the BaTi1-xScxO3-x/2 (0.5 ≤ x ≤ 0.7) materials retain their cubic structures upon full saturation by protons and show no signs of chemical instability upon exposure to 1 atm H2O(g) down to 100 °C. The BaTi1-xScxO3-x/2 materials with 0.5 ≤ x ≤ 0.7 may therefore find application in, for instance, steam electrolysis or similar processes involving high water vapor pressures.

Sr2GaScO5, Sr10Ga6Sc4O25, and SrGa0.75Sc0.25O2.5: a play in the octahedra to tetrahedra ratio in oxygen-deficient perovskites.

Three different perovskite-related phases were isolated in the SrGa(1-x)Sc(x)O(2.5) system: Sr(2)GaScO(5), Sr(10)Ga(6)Sc(4)O(25), and SrGa(0.75)Sc(0.25)O(2.5). Sr(2)GaScO(5) (x = 0.5) crystallizes in a brownmillerite-type structure [space group (S.G.) Icmm, a = 5.91048(5) Å, b = 15.1594(1) Å, and c = 5.70926(4) Å] with complete ordering of Sc(3+) and Ga(3+) over octahedral and tetrahedral positions, respectively. The crystal structure of Sr(10)Ga(6)Sc(4)O(25) (x = 0.4) was determined by the Monte Carlo method and refined using a combination of X-ray, neutron, and electron diffraction data [S.G. I4(1)/a, a = 17.517(1) Å, c = 32.830(3) Å]. It represents a novel type of ordering of the B cations and oxygen vacancies in perovskites. The crystal structure of Sr(10)Ga(6)Sc(4)O(25) can be described as a stacking of eight perovskite layers along the c axis ...[-(Sc/Ga)O(1.6)-SrO(0.8)-(Sc/Ga)O(1.8)-SrO(0.8)-](2).... Similar to Sr(2)GaScO(5), this structure features a complete ordering of the Sc(3+) and Ga(3+) cations over octahedral and tetrahedral positions, respectively, within each layer. A specific feature of the crystal structure of Sr(10)Ga(6)Sc(4)O(25) is that one-third of the tetrahedra have one vertex not connected with other Sc/Ga cations. Further partial replacement of Sc(3+) by Ga(3+) leads to the formation of the cubic perovskite phase SrGa(0.75)Sc(0.25)O(2.5) (x = 0.25) with a = 3.9817(4) Å. This compound incorporates water molecules in the structure forming SrGa(0.75)Sc(0.25)O(2.5)·xH(2)O hydrate, which exhibits a proton conductivity of ∼2.0 × 10(-6) S/cm at 673 K.

Scheelite type Sr1-xBaxWO4 (x = 0.1, 0.2, 0.3) for possible application in Solid Oxide Fuel Cell electrolytes.

Polycrystalline scheelite type Sr1-xBaxWO4 (x = 0.1, 0.2 & 0.3) materials were synthesized by the solid state sintering method and studied with respect to phase stability and ionic conductivity under condition of technological relevance for SOFC applications. All compounds crystallized in the single phase of tetragonal scheelite structure with the space group of I41/a. Room temperature X-ray diffraction and subsequent Rietveld analysis confirms its symmetry, space group and structural parameters. SEM illustrates the highly dense compounds. Significant mass change was observed to prove the proton uptake at higher temperature by TG-DSC. All compound shows lower conductivity compared to the traditional BCZY perovskite structured materials. SBW with x = 0.3 exhibit the highest ionic conductivity among all compounds under wet argon condition which is 1.9 × 10-6 S cm-1 at 1000 °C. Since this scheelite type compounds show significant conductivity, the new series of SBW could serve in IT-SOFC as proton conducting electrolyte.

The influence of cation ordering, oxygen vacancy distribution and proton siting on observed properties in ceramic electrolytes: the case of scandium substituted barium titanate.

The origin of the 2-order of magnitude difference in the proton conductivity of the hydrated forms of hexagonal and cubic oxygen deficient BaScxTi1-xO3-δ (x = 0.2 and x = 0.7) was probed using a combination of neutron diffraction and density functional theory techniques to support published X-ray diffraction, conductivity, thermogravimetric and differential scanning calorimetry studies. Cation ordering is found in the 6H structure type (space group P63/mmc) adopted by BaSc0.2Ti0.8O3-δ with scandium preferentially substituting in the vertex sharing octahedra (2a crystallographic site) and avoiding the face-sharing octahedra (4f site). This is coupled with oxygen vacancy ordering in the central plane of the face-sharing octahedra (O1 site). In BaSc0.7Ti0.3O3-δ a simple cubic perovskite (space group Pm3[combining macron]m) best represents the average structure from Rietveld analysis with no evidence of either cation ordering or oxygen vacancy ordering. Significant diffuse scattering is observed, indicative of local order. Hydration in both cases leads to complete filling of the available oxygen vacancies and permits definition of the proton sites. We suggest that the more localised nature of the proton sites in the 6H structure is responsible for the significantly lower proton conduction observed in the literature. Within the 6H structure type final model, proton diffusion requires a 3-step process via higher energy proton sites that are unoccupied at room temperature and is also likely to be anisotropic whereas the highly disordered cubic perovskite proton position allows 3-dimensional diffusion by well-described modes. Finally, we propose how this knowledge can be used to further materials design for ceramic electrolytes for proton conducting fuel cells.

Crystal structure and proton conductivity of BaSn0.6Sc0.4O3-δ : insights from neutron powder diffraction and solid-state NMR spectroscopy.

The solid-state synthesis and structural characterisation of perovskite BaSn1-x Sc x O3-δ (x = 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space group Pm3m) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. 119Sn and 45Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D2O. It also indicates that the Sn4+ and Sc3+ local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (x ≤ 0.2) and in the tin coordination shell at high concentrations (x ≥ 0.3). 17O NMR spectra on 17O enriched BaSn1-x Sc x O3-δ materials show the existence of Sn-O-Sn, Sn-O-Sc and Sc-O-Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn0.6Sc0.4O3-δ refines the deuteron position at the 24k crystallographic site (x, y, 0) with x = 0.579(3) and y = 0.217(3) which leads to an O-D bond distance of 0.96(1) Å and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10-4 to 1.1 × 10-3 S cm-1 between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature.

Factor XIII and tissue transglutaminase antibodies in coeliac and inflammatory bowel disease.

Tissue transglutaminase (tTg) has been identified as an autoantigen in coeliac disease (CD). There is a marked homology between different forms of transglutaminase, such as tTg and coagulation factor XIII. We compared titres of both IgA- and IgG-antibodies against these two antigens in 20 CD patients, 20 endomysial antibody (EMA)-negative controls and a group with inflammatory bowel disease (34 with Crohn's disease and 23 with ulcerative colitis). IgA-antibodies against tTg correlated with EMA titres and had high sensitivity and specificity in screening for CD. Only in two CD patients were high titres found of IgA-antibodies against factor XIII, non-reactive with tTg. Both lacked bleeding tendency. The presence of IgG-antibodies against tTg, in contrast, had low sensitivity and specificity in screening for CD and were frequently seen in inflammatory bowel disease. Similarly, factor XIII IgG-antibodies displayed a non-specific pattern with modestly elevated titres in patients with Crohn's disease and in both EMA-negative and positive patients. Despite a marked homology with tTg, the occurrence of high titre IgA-antibodies against factor XIII is infrequent in CD, but may-when present-be the result of epitope spreading. The presence of IgG-antibodies in CD and inflammatory bowel disease illustrates the complexity of autoantibody reactions in gastrointestinal disease.

Nutritional status and muscle strength in patients with emphysema and severe alpha(1)-antitrypsin deficiency.

BACKGROUND: The association between emphysema and weight loss is well known. Severe alpha(1)-antitrypsin deficiency is an important risk factor for the development of emphysema. STUDY OBJECTIVE: To study nutritional status and muscle strength in patients with severe alpha(1)-antitrypsin deficiency and emphysema. METHODS: Fifteen alpha(1)-antitrypsin-deficient patients with emphysema (7 men) and 18 healthy control subjects (9 men) were included in the study. Total body protein (TBP) was measured by in vivo neutron activation analysis of nitrogen. Lean body mass (LBM) was estimated from measurement of total body potassium. In analogy with body mass index (BMI), TBP index and LBM index were calculated as TBP/height squared and LBM/height squared, respectively. Respiratory muscle strength was studied by maximal inspiratory pressure (PImax) and maximal expiratory pressure (PEmax), and skeletal muscle strength by handgrip test. Plasma albumin, transthyretin, and retinol-binding protein concentrations were analyzed as biochemical markers of nutritional status. RESULTS: In the alpha(1)-antitrypsin-deficient individuals, lung function test results were consistent with severe chronic airway obstruction, whereas the healthy control subjects had normal lung function. No significant differences were found in age, body weight, or BMI between the groups. TBP (p < 0.05), TBP index (p < 0.001), LBM index (p < 0.05), and plasma concentration of transthyretin (p < 0.01) were significantly lower in the patients than in the control subjects. There was a significant correlation between TBP and LBM (p < 0.001), and between TBP and body weight (p < 0.001). In the male subgroup, PImax (p < 0.05) and PEmax (p < 0.05) were significantly lower in the patients than in the control subjects. In the female subgroup, handgrip strength was significantly lower in the patients than in the control subjects (p < 0.05). Body weight was significantly correlated with handgrip test (p < 0.05) in the male patients. In the female patients, body weight was significantly correlated with PImax (p < 0.05), LBM with PEmax (p < 0.05), and LBM with handgrip test (p < 0.01). CONCLUSION: Reduced TBP and plasma transthyretin concentration in alpha(1)-antitrypsin-deficient patients with emphysema may indicate early signs of malnutrition.

The Hume-Rothery Compound Mn8 Ga27.4 Zn13.6 : Separated Zn13 -Clusters Interspersed in a Primitive Cubic Host Lattice.

Separated Zn13 cluster entities unexpectedly occur in the solid-state structure of Mn8 Ga27.4 Zn13.6 (the central building block is shown). They correspond to centered cuboctahedra, that is, small volumes of face-centered cubic metal. The intriguing segregation of Ga and Zn atoms in Mn8 Ga27.4 Zn13.6 was verfied by Rietveld refinement of neutron powder diffraction data.

Proton conductivity of hexagonal and cubic BaTi1-xScxO3-δ (0.1 ≤x≤ 0.8).

BaTi1-xScxO3-δ (x = 0.1-0.8) was prepared via solid state reaction. High resolution X-ray powder diffraction was used to characterise the synthesised materials. It was found that low substitution (x = 0.1 and 0.2) of Ti(4+) for Sc(3+) gives a hexagonal perovskite structure, whereas high substitution (x = 0.5-0.7) results in a cubic perovskite structure. Thermogravimetric analysis revealed significant levels of protons in both as-prepared and hydrated samples. Electrical conductivity was measured by AC impedance methods under oxygen, argon and under dry and humid, both H2O and D2O, conditions for BaTi1-xScxO3-δ (x = 0.2, 0.6 and 0.7). In the temperature range of 150-600 °C, under humid conditions, the conductivity is significantly higher than that under the dry conditions. The increase in conductivity is especially prominent for the cubic phases, indicating that protons are the dominant charge carriers. The proton conductivity of hexagonal BaTi0.8Sc0.2O3-δ is approx. two orders of magnitude lower than that of the more heavily substituted cubic phases. Conductivity is also found to be higher in dry O2 than in Ar in the whole temperature range of 150-1000 °C, characteristic of a significant contribution from p-type charge carriers under oxidising atmospheres. Greater Sc(3+) substitution leads to a higher proton concentration and the highest proton conductivity (σ∼ 2 × 10(-3) S cm(-1) at 600 °C) is found for the BaTi0.3Sc0.7O3-δ composition.

The proton conducting electrolyte BaTi0.5In0.5O2.75: determination of the deuteron site and its local environment.

Deuterated BaTi0.5In0.5O2.75 has been studied with neutron total (Bragg plus diffuse) scattering data, using both the Rietveld refinement method and the reverse Monte Carlo (RMC) modelling technique, to investigate the preferred proton site and its local structural environment. The Rietveld analysis shows an excellent fit between experimental data and a long-range cubic description of the BaTi0.5In0.5O2.53(OD)0.44 perovskite structure containing a statistical distribution of Ti and In ions at the centre of regular (Ti/In)O6 octahedra. However, an RMC analysis of the data reveals substantial local structural features that reflect limitations of the Rietveld method for studies of this type. The Ti-O and In-O pair distribution functions given by the RMC analysis are markedly different from each other, with average Ti-O and In-O bond distances of 2.035 Å and 2.159 Å, respectively. The InO6 octahedra are regular in shape whereas the TiO6 octahedra are distorted. The average O-D bond distance is roughly 0.96 Å, and the preferred deuteron sites have a second nearest oxygen distance of 2.13 Å, which confirms localized tilting of the deuteron and indicates a substantial degree of hydrogen bonding. The impact of octahedral distortion and hydrogen bonding on the proton conduction mechanism is discussed.

Local structural properties of 0.5BiMnO3-0.5ATiO3 (A = Ba or Sr).

Neutron total scattering data have been used to probe the long- and short-range structure of 0.5BiMnO(3)-0.5ATiO(3) (A = Ba or Sr). Modelling of the total scattering data, using the reverse Monte Carlo (RMC) method, reveals local disorder that differs substantially from the average structure. Significantly, the Bi(3+) cations prefer to adopt an asymmetric coordination due to the influence of the lone-pair electrons.

Neutron total scattering study of the delta and beta phases of Bi2O3.

The highly disordered structure of the delta phase of Bi2O3, which possesses the highest known oxide-ion conductivity, has been studied using neutron powder diffraction. A detailed analysis of data collected at 1033(3) K using Rietveld refinement indicates that the time-averaged structure of delta-Bi2O3 can be described using the accepted model of a disordered, anion-deficient fluorite structure in space group Fm3m. However, reverse Monte Carlo modelling of the total (Bragg plus diffuse) scattering demonstrates that the local anion environment around the Bi3+ resembles the distorted square pyramidal arrangement found within the stable alpha and metastable beta phases at ambient temperature, which is characteristic of the cation's 6s2 lone-pair configuration. Similarities between the structures of the highly disordered delta phase and the ambient temperature metastable beta phase are used to support this assignment and assess the validity of previous structural models based on short-range ordering of vacancies within the cubic lattice of delta-Bi2O3.

Detection of circulating and endothelial cell polymers of Z and wild type alpha 1-antitrypsin by a monoclonal antibody.

Globular inclusions of abnormal alpha1-antitrypsin (AAT) in the endoplasmic reticulum of hepatocytes are a characteristic feature of AAT deficiency of the PiZZ phenotype. Monoclonal antibodies, which contain constant specificity and affinity, are often used for the identification of Z-mutation carriers. A mouse monoclonal antibody (ATZ11) raised against PiZZ hepatocytic AAT was successfully used in enzyme-linked immunosorbent assays (ELISA) and in identification of Z-related AAT globular inclusions by immunohistochemical techniques. Using electrophoresis, Western blotting, and ELISA procedures, we have shown in the present study that this monoclonal antibody specifically detects a conformation-dependent neoepitope on both polymerized and elastase-complexed molecular forms of AAT. The antibody has no apparent affinity for native, latent, or cleaved forms of AAT. The antibody ATZ11 illustrates the structural resemblance between the polymerized form of AAT and its complex with elastase and provides evidence that Z-homozygotes beyond the native form may have at least one more circulating molecular form of AAT, i.e. its polymerized form. In addition, staining of endothelial cells with ATZ11 antibody in both M- and Z-AAT individuals shows that AAT attached to endothelial cells is in a polymerized form. The antibody can be a powerful tool for the study of the molecular profile of AAT, not only in Z-deficiency cases but also in other (patho)physiological conditions.

Analysis of systemic biomarkers in COPD patients.

The finding that alphal-antitrypsin (AAT) deficiency, PiZZ, a well-established genetic risk factor for COPD, is related to high levels of circulating AAT polymers, prompted us to measure serum levels of such polymers and selected markers of inflammation in age- and gender-matched patients with stable COPD and control subjects with and without severe AAT deficiency, and to assess their relationship with each other and with the genetic AAT-variant. We found that COPD individuals (n= 20), independent of AAT-variant, had significantly higher serum levels of AAT and its polymers, MMP-9, sICAM-1, VEGF and sE-selectin than controls (n=30). Subjects with PiZZ COPD (n= 10) showed significantly elevated serum levels of AAT-polymers, sE-selectin and sICAM-1, while patients with PiMM COPD (n= 10) showed higher levels of MMP-9, VEGF, IL-8 and MCP-1 than controls. By using factor analysis we were able to split the analysed biomarkers into two independent components: the first containing MMP-9, MCP-1, IL-8 and VEGF and the second-AAT and its polymers and sE-selectin. The result from the binomial logistic regression showed that 95.2 percent of the control individuals and 94.7 percent of the COPD patients can be correctly classified on the basis of the measured serum biomarkers. These observations highlight the importance of the finding sets of biomolecules, which could offer new strategies for the diagnosis of COPD and may have value for monitoring progression of COPD.