Controlled Gas Atmospheres Research Articles

Low-pressure ETEM Studies of Au assisted MgO Nanorod Growth

Environmental transmission electron microscopy (ETEM) studies MgO nanorod growth from Au catalyst nanoparticles in a controlled gas atmosphere have been performed, in order to elucidate the mobility of Au surface atoms and the configuration of the Au/MgO interface. MgO nanorod growth is driven by the electron beam and found to be strongly dependent on the gaseous environment in the microscope and electron beam current density.

Effect of oxygen adsorption on surface tension of liquid copper: Experiments and thermodynamic models

• The effect of oxygen on the surface tension of liquid Cu was investigated. • The adsorption behavior of oxygen is presented with a thermodynamic model. • This model assumes a hypothetical binary system of Cu-“Cu 2 O”. • “Cu 2 O” is considered as an associate molecule. • Ideal adsorption model exhibits the best fit of the experimental results. The effect of oxygen adsorption on surface tension of liquid copper at two different temperatures (1390 and 1440 K) has been investigated. A combination of specially designed crucibles, He-Ne laser, and high-resolution photography in a highly controlled gas atmosphere was used for accurate measurements. Experimental data exhibits decreasing surface tension with increasing oxygen partial pressure. Discussion on the adsorption behavior of oxygen is presented based on thermodynamic models by assuming a hypothetical binary system of Cu-“Cu 2 O”, in which “Cu 2 O” is considered as an associate molecule. Ideal adsorption model which assumes insignificant interactions between Cu and Cu 2 O on the surface exhibits the best fit to the experimental results.

Mechanical characterisation of heat resistant power plant materials by creep and fatigue testing in controlled gas atmospheres

The continuing increase of steam parameters of fossil fuelled high efficiency power plants and new combustion concepts for the capture and storage of carbon dioxide lead to harsher service conditions for the components and structural materials of such facilities. The present work introduces a test concept that allows testing of candidate materials under simultaneous mechanical and corrosive loading. The material's reaction can be directly investigated under simulated temperature, load and corrosion conditions of modern installations. First results obtained for different heat resistant steels suggest a strong influence of the environmental medium on the fatigue and creep behaviour. Such findings complement the data that is available from the classical qualification process of the materials and may support the material selection for new power plant installations.

High temperature in situ neutron powder diffraction of oxides

Neutron powder diffraction (NPD) is a powerful tool for the characterization of oxides. Unlike X-ray diffraction where scattering occurs from the electron cloud, neutrons interact with the atomic nucleus enabling direct characterization of the oxygen sublattice. This reveals critical information related to the location, number, and mobility of oxygen anion vacancies and interstitials in hypo- and hyper-stoichiometric oxides. This review examines the growing use of in situ NPD to characterize materials for oxygen anion transport and oxygen storage in fuel cells, ion transport membranes, and as catalysts and catalyst supports. Typical measurement temperatures range between room temperature and 1200 °C, under vacuum or in controlled gas atmospheres from pure oxygen to dilute hydrogen.

52 HYALURONIC ACID IMPROVES CRYOTOLERANCE OF BUFFALO (BUBALUS BUBALIS) IN VITRO-DERIVED EMBRYOS

Although in vitro embryo production efficiency in buffalos has greatly improved over the years, the in vitro-produced embryos show lower viability and resistance to cryopreservation. Therefore, it is necessary to optimize the in vitro culture conditions to improve embryo quality. Hyaluronic acid, a glycosaminoglican present in oviducal and uterine fluids, has been shown to successfully support in vitro development of bovine embryos (Stojkovic et al. 2002 Reproduction 124, 141–153). The aim of this study was to evaluate the influence of high concentrations of hyaluronic acid (HA) during late in vitro culture on blastocyst development, as well as on their cryotolerance after cryotop vitrification in buffalos. In vitro matured and fertilized buffalo oocytes (n = 1007) from slaughterhouse ovaries were cultured for 4 days in SOFaa supplemented by 8 mg mL–1 of BSA in a controlled gas atmosphere consisting of 5% CO2, 7% O2 and 88% N2, in humidified air, at 38.5°C. On Day 4, cleavage rate was assessed (75.2%) and all of the cleaved elements were divided into 3 different late culture groups: 8 mg mL–1 of BSA (n = 244; group A), 8 mg mL–1 of BSA supplemented by 6 mg mL–1 of HA (n = 251; group B) and 1 mg mL–1 of BSA supplemented by 6 mg mL–1 of HA (n = 262; group C). On Day 7 after IVF, embryo outcome was assessed and all of the embryos were vitrified by cryotop [De Rosa et al. 2007 Ital. J. Anim. Sci. 6 (Suppl 2), 747–750] and cultured for 24 h. The resistance to cryopreservation was evaluated by assessing the survival rate on the basis of morphological criteria and the percentage of embryos reaching a more advanced developmental stage after 24 h culture. Data were analysed by the chi-square test. No differences in blastocyst rate were recorded among groups (43.9, 44.3 and 40.0%, respectively in A, B and C groups). However, out of the total embryos, a higher percentage of Grade 1 hatched blastocysts (Robertson and Nelson 1998 Manual of the International Embryo Transfer Society 9, 103–16) was observed in group C (P < 0.05) than in groups A and B (14.3, 18.8 and 25.5% in A, B and C groups, respectively). Although the supplementation with HA did not improve the survival rates following vitrification-warming (51.1, 59.4 and 58.4% in A, B and C groups, respectively), the percentage of vitrified-warmed embryos that resumed development and reached a more advanced developmental stage after culture increased (P < 0.01) in group C (20.7, 27.7 and 37.6% in A, B and C groups, respectively). In conclusion, the addition of 6 mg mL–1 of HA, together with a limited protein source (i.e. 1 mg mL–1 of BSA), during late culture improved buffalo embryo quality, indicated by both the greater percentage of advanced-stage embryos and by the resumption of development after post-warming culture.

Use of Modified Atmosphere Packaging to Preserve Mushroom Quality during Storage

Mushrooms have attracted much attention due to their excellent nutritional and sensory properties. However, they are highly perishable and rapidly lose their organoleptic characteristics. Many methods have been employed for mushroom storage, such as packaging, blanching, canning, or freeze drying. Among them, modified atmosphere packaging (MAP) has been widely employed for preserving fresh mushrooms. MAP provides an affordable packaging system that partly avoids enzymatic browning, fermentation and other biochemical processes by maintaining a controlled gas atmosphere. Several factors, including optimum CO2 and O2 partial pressures, permeability, package material, thickness, or product weight, must be considered in order to design a suitable modified atmosphere package for mushrooms. Thus, different strategies are available to preserve mushroom quality after harvest. The article presents some promising patents on use of modified atmosphere packaging to preserve mushroom quality during storage.

Phase Separation at the Nanoscale: Structural Properties of BaO Segregates on MgO-Based Nanoparticles

Composite BaO/MgO nanoparticles have been prepared by chemical vapor synthesis and subsequent annealing in controlled gas atmospheres. High resolution transmission electron microscopy and X-ray diffraction reveal that a part of the obtained nanoparticles can be characterized as support particles with hemispherical BaO phases. The structural and energetic properties of BaO units dissolved inside the MgO host and adsorbed on MgO(100) were investigated by density functional theory (DFT) calculations. Moreover, ab initio thermodynamics was used to explore the shape of BaO and MgO particles in a water environment as a function of temperature. The calculations suggest that the spherical shapes of the segregates result from the growth process and become thermodynamically stabilized by surface hydroxylation.

Structural and electrical properties of BaCe(Ti,Y)O3 protonic conductors

Barium cerate exhibits high protonic conductivity, especially when doped by suitable trivalent ions. A possible approach to get the protonic conductor stable in the presence of CO2 with relatively high protonic conductivity is the preparation of solid solutions of BaCe1−xMexO3−δ (Me=Zr, Ti) doped simultaneously with acceptor ion. In this work selected properties of series of Ba(Ce0.95Ti0.05)1−yYyO3−δ (0≤y≤0.2) materials prepared by solid-state reaction method were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and direct current (DC) electrical measurements, including open cell voltage (OCV) measurements of electrochemical cells were used as experimental techniques. Structural studies have shown materials crystallized in orthorhombic Pmcn phase with the solubility limit of Y in Ba(Ce0.95Ti0.05)1−yYyO3−δ higher than 20at.%. The DC conductivity measurements accompanied by the potentiometric OCV measurements of solid state electrochemical cells in controlled gas atmospheres (containing H2, O2 and H2O) and temperatures (500–800°C) allowed determination of total electrical conductivity and transference numbers of oxygen, protonic and electronic defects in prepared materials. The introduction of Y increases total electrical conductivity and transference numbers for protonic defects, which was correlated with structural changes.

Diffusion and oxidation phenomena at elevated temperatures in the contact area between hardened steel and various PVD coatings

Growing cost reduction trends in machining applications has led to a significant increase of cutting speeds and process temperatures. In this way, oxidation and diffusion mechanisms in the contact area between chip and tool become substantial, affecting the tool performance.In this paper, diffusion and oxidation interactions at 800°C among various PVD coated cemented carbide inserts, hardened steel counterparts and low oxygen atmosphere will be introduced. The experiments were conducted under adjustable ambient conditions by a device, developed for this purpose. The coated specimens were fastened inside an electrical heating unit in a controlled gas atmosphere, allowing their contact with steel specimens at a desired pressure and temperature. During the experiments, periodic intervals of the applied pressure were followed by brief non-contact pauses, to avoid any permanent welding between coating and counterpart. For providing insight on the effect of diffusion and oxidation on the films' chemical composition and mechanical properties, coatings' cross sections in the film contact area were investigated by EDX-line scanning. The results show a considerable deterioration of the films' mechanical properties, which can be attributed more to coatings' oxidation and less to diffusion.

124 CO-CULTURE WITH BOVINE INTACT CUMULUS - OOCYTE COMPLEXES DURING IN VITRO FERTILIZATION OF BUFFALO DENUDED OOCYTES COMPLETELY RESTORES THEIR FERTILIZING AND DEVELOPMENTAL COMPETENCE

Removal of cumulus cells is necessary for several technologies such as vitrification, intracytoplasmic sperm injection, and nuclear transfer. However, it is known that the presence of cumulus cells during IVF of buffalo oocytes is fundamental for fertilization and embryo development (Gasparrini et al. 2007 Anim. Reprod. Sci. 98, 335–342; Nandi et al. 1998 Theriogenology 50, 1251–1262). The aim of this work was to evaluate whether co-culture with intact bovine cumulus–oocyte complexes (COC) during IVF would restore the developmental competence of denuded buffalo oocytes. Due to the scarce availability of buffalo ovaries, the somatic support was provided by bovine cumulus cells. Abattoir-derived COC were matured in vitro according to our standard procedures (Gasparrini et al. 2006, Theriogenology, 65, 275–287) and randomly distributed in 3 fertilization groups: 1) a control group of COC (n = 122), 2) a negative control of denuded oocytes (DO; n = 119), and 3) DO co-cultured with in vitro matured bovine COC (DO+COC; n = 103) in a 1:1 ratio (3 bovine COC + 3 denuded buffalo oocytes/50 μL drop). Fertilization was carried out with frozen–thawed spermatozoa from a tested bull in TALP medium supplemented by 0.2 mM penicillamine, 0.1 mM hypotaurine, and 0.01 mM heparin at 38.5°C under a controlled gas atmosphere of 5% CO2 in humidified air. After fertilization the zygotes were cultured in SOF medium including essential and nonessential amino acids and 8 mg mL–1 BSA, at 38.5°C under humidified 5% CO2, 7% O2, and 88% N2, up to the blastocyst stage. On Day 5 and on Day 7 (Day 0 = IVF) cleavage and blastocyst rates were respectively recorded. Data were analysed by chi-square test. As expected, cleavage and blastocyst rates were lower (P < 0.01) in DO (36.1 and 9.2%, respectively) compared with the control (67.2 and 27.1%, respectively). However, co-culture during IVF (DO+COC) significantly increased (P < 0.01) both parameters compared with DO, giving cleavage (70.9%) and blastocyst (27.2%) rates similar to the control. The results of this study demonstrated that co-culture with bovine intact COC during IVF of buffalo denuded oocytes completely restores their fertilizing capability and blastocyst developmental competence. We conclude that this may be a suitable strategy for preserving the developmental competence of oocytes devolved to technologies, such as oocyte vitrification, that require cumulus removal.

Effect of TiO2‐content on Reduction of Iron Ore Agglomerates

The effect of titanium oxide on iron ore agglomerates is studied by the use of test sinter, test pellets and synthetic briquettes under laboratory conditions. Titanium favours secondary hematite rather than magnetite, which is the main phase in the sinter of Rautaruukki's Raahe plant. Additionally, the effects of sinter RDI and pellet LTD on the blast furnace process are evaluated using the test results of basket trials in LKAB's Experimental Blast Furnace. The effect of titanium in synthetic hematite is studied as hematite is reduced to magnetite in the RDI test. This occurrence causes deterioration in burden permeability. Synthetic titanium-bearing iron oxides under controlled conditions are investigated at the University of Oulu. The effect of TiO2, in solid solution in magnetite, on the magnetite to hematite oxidation is studied separately in order to simulate the final stage of the sintering process. In other experiments, hematite samples doped with various contents of TiO2 are studied using thermogravimetry under a controlled gas atmosphere (CO/CO2/H2/N2). The TiO2 content of hematite has a clear effect on reduction degradation. Also increasing content of TiO2 in solid solution in magnetite radically accelerates the oxidation rate. In the pilot tests, TiO2 content has a similar negative effect on the reduction strength of both sinter and pellets

When Fewer Photons Do More: A Comparative O2Photoadsorption Study on Vapor-Deposited TiO2and ZrO2Nanocrystal Ensembles

The charge separation properties of TiO2 and ZrO2 nanocrystal powders which were produced by metal organic chemical vapor phase deposition were compared by means of O2 photoadsorption. Prior to the UV excitation experiments, we carefully explored the structure and morphology as well as the spectroscopic properties of the dehydroxylated nanoparticles in controlled gas atmospheres using UV diffuse reflectance, FT-IR, and electron paramagnetic resonance spectroscopy. On the basis of this information, we utilized the photogeneration of surface-adsorbed O2− radicals and their detection by EPR spectroscopy to quantify the concentration of separated charges and to relate these figures to the number of oxide particles that were exposed to known numbers of UV photons with defined energies. The results presented in this study reveal that upon band-gap excitation, ZrO2 nanoparticles are by 2 orders of magnitude more efficient in oxygen-assisted charge separation than TiO2. The dramatically diminished charge separation yield in TiO2 is attributed to the existence of deep trap states which persistently stabilize paramagnetic holes and at the same time act as recombination centers. Their absence in ZrO2 nanocrystals gives rise to a comparable performance in terms of photoadsorbed O2 and essentially compensates for the significantly wider optical band gap in relation to TiO2.

Structural and electrical properties of (Ba1−xSrx)(Zr0.9M0.1)O3, M=Y, La, solid solutions

The aim of the work was to study the structural and electrical properties of the (Ba 1− x Sr x )(Zr 0.9 Y 0.1 )O 3 and (Ba 1− x Sr x )(Zr 0.9 Y 0.1 )O 3 solid solutions. The powders of different strontium content ( x = 0, 0.03, 0.05 and 0.1) were prepared by a thermal decomposition of organo-metallic precursors containing ethylenediaminetetraacetate acid. Some parameters describing stability and transport properties of the perovskite structure, such as tolerance factor, specific free volume and global instability index, were calculated. It was found that the introduction of strontium into both solid solutions caused the increase of specific free volume and global instability index—these structures became a little less stable but, on the other hand, better ionic conductor. All samples were cubic perovskite and the substitution of strontium for barium caused the decrease of respective lattice parameters. Electrical conductivity measurements were performed by the d.c. four-probe method in controlled gas atmospheres containing Ar, air, H 2 and/or H 2 O at the temperature from 300 to 800 °C. It was found that the conductivity depended on a chemical composition of the samples and the atmosphere. In general, the electrical conductivity was higher in wet atmospheres which contained oxygen, being in accordance with the model of a proton transport in the perovskite structure which assumed the presence of the oxygen vacancy. The solid solution containing 5 mol.% of strontium showed the highest conductivity and the lowest activation energy of conductivity regardless of the atmospheres.

Photoluminescent Nanoparticle Surfaces: The Potential of Alkaline Earth Oxides for Optical Applications

The surfaces of alkaline earth oxides emit bright, colored light and have potential as thermally stable inorganic phosphors with adsorption-dependent optical properties. The doping of thermally stable MgO nanocubes with low-coordinated BaO surface elements (see figure) clearly demonstrates that chemical manipulation of the solid–gas interface provides an efficient means to adjust the optical properties of powders in controlled gas atmospheres.

220 SYNERGISTIC EFFECT ON EMBRYO DEVELOPMENT BY INCLUSION OF SUPPLEMENTAL EMBRYOS IN AGAR CHIPS

The main scope of this study was to evaluate the likelihood of a helper effect of agar-embedded cleaved embryos on a low number of free embryos at a similar stage of development within the same culture droplet. Such an improved system could be beneficial within ovum pickup/in vitro embryo production (OPU/IVEP) combined protocols whenever a low number of OPU-derived cleaved embryos are produced per donor. Oocytes were recovered from abattoir ovaries, and after in vitro maturation (IVM) and in vitro fertilization (IVF), presumptive zygotes were deprived of cumulus investment and allocated into culture droplets for 24 h. At 48 h from IVF, 4- to 8-cell cleaved embryos were randomly allocated into a control and a treatment group. Control groups consisted of 1, 3, 5, and 10 embryos, respectively, in 50-μL droplets. Treatment groups consisted of 1, 3, and 5 free embryos with the addition of 9, 7, and 5 embryos, respectively, at a similar stage of development embedded in agar chips, so as to reach a total number of 10 cleaved embryos in each culture droplet. Culture was performed for both the control and treatment groups in SOF medium droplets covered with mineral oil, with the supplementation of essential and nonessential amino acids in a controlled gas atmosphere consisting of 5% CO2, 7% O2, and 88% N2 at 39°C. Final embryo output was checked at Day 7 from IVF. When considering only free embryos, the difference in progression to blastocyst development was highly significant between the control and treatment groups: 1) group 1 v. 1 + 9: 6.6 v. 84.3% (P = 0.00000); 2) group 3 v. 3 + 7: 11.1 v. 41.3% (P = 0.00001); 3) group 5 v. 5 + 5: 24.4 v. 42.2% (P = 0.00001). Rate of blastocyst development in the control group containing 10 cleaved embryos was not significantly different from free cleaved embryos in the 3 + 7 (39.2 v. 41.3%, P = 0.71) and 5 + 5 treatment groups (39.2 v. 42.2%, P = 0.54), but was significantly lower when compared with the 1 + 9 treatment group (39.2 v. 84.3%, P = 0.000). For 1, 3, 5, and 10 control group embryos, the numbers of replicates and total cleaved embryos used (n) were 30 (n = 30), 27, (n = 81), 27 (n = 135), and 39 (n = 390), respectively. For the 1 + 9, 3 + 7, and 5 + 5 treatment group embryos, the numbers of replicates and total cleaved embryos used were 32 (n = 32), 29 (n = 87), and 27 (n = 135), respectively. In conclusion, a beneficial effect of agar-embedded embryos on the development of free embryos within the same culture droplet was shown. A striking improvement in late-stage embryo development was particularly evident when considering the 1 v. 1 + 9 control and treatment groups. These results may foster a different strategic approach in in vitro culture to enhance embryo development from highly valuable donors.

205 EFFECT OF OSTEOPONTIN ON CLEAVAGE AND BLASTOCYST RATES IN BUFFALO SPECIES (BUBALUS BUBALIS)

It was previously reported that osteopontin (OPN), an acidic single-chain phosphorylated glycoprotein found in the oviductal fluid in cattle (Gabler C et al. 2003 Reproduction 126, 721–729), is able to facilitate fertilization in this species (Gasparrini B et al. 2008 Reprod. Fertil. Dev. 20(Suppl. I), 180 abst). The present study aimed to investigate whether the addition of OPN to the fertilization medium would affect both cleavage and postfertilization embryo development in the buffalo. To assess the influence of OPN on cleavage and blastocyst rates, in vitro-matured oocytes were fertilized in modified Tyrode’s albumin lactate pyruvate medium (Lu KH et al. 1987 Vet. Rec. 121, 259–260) supplemented with penicillamine, hypotaurine, and heparin, in the presence of 0.0 (n = 258), 0.1 (n = 263), 1 (n = 261), and 10 μg mL–1 (n = 264) of OPN. In vitro fertilization was carried out with frozen–thawed spermatozoa from a bull already tested for IVF. After 20 to 22 h of co-incubation at 38.5°C and 5% CO2 in air, putative zygotes were gently pipetted to remove cumulus cells, washed, and transferred, 10 per droplet, into 20 μL of SOF medium including essential and nonessential amino acids and BSA (Tervit HR et al. 1972 J. Reprod. Fertil. 30(3), 493–497), in a controlled gas atmosphere consisting of 5% CO2, 7% O2, and 88% N2, in humidified air, at 38.5°C. The culture medium was changed on Day 5 (Day 0 = day of insemination), when cleavage rate was assessed and embryos were moved into fresh medium for an additional 2 days. On Day 7, development rates into blastocysts of superior quality were recorded. Differences in the percentages of both cleavage and blastocyst rates among groups were analyzed by chi-square test. Significantly higher cleavage rates (59.3, 70.3, 71.6, and 42.4%, respectively, in the control group and in the groups with 0.1, 1, and 10 μg mL–1 of OPN; P < 0.01) were observed in the groups with 0.1 and 1 μg mL–1 of OPN compared with the other groups. Likewise, higher blastocyst rate percentages (17.4, 27.4, 29.9, and 9.5%, respectively, in the control group and in the groups with 0.1, 1, and 10 μg mL–1 of OPN; P < 0.01) were observed in the groups with 0.1 and 1 μg mL–1 of OPN compared with the other groups. In conclusion, these results showed that addition of low concentrations of OPN in the fertilization medium improved both cleavage and postfertilization embryo development in the buffalo, whereas the higher concentration resulted in impaired late-stage embryo development.

Ceramic electrolytes based on (Ba1 − x Ca x )(Zr0.9Y0.1)O3 solid solution

The aim of this work was to study the electrical and electrochemical properties of the (Ba1 − xCax)(Zr0.9Y0.1)O3 solid solutions. The powders of different calcium content (x = 0, 0.05, 0.1, and 1) were prepared by a thermal decomposition of organo-metallic precursors containing ethylenediaminetetraacetate acid. X-ray diffraction analysis showed that a small substitution of calcium for barium caused formation of cubic solid solutions with the decreasing cell parameters. Electrical conductivity measurements were performed by the d.c. four-probe method in controlled gas atmospheres containing Ar, air, H2, and/or H2O at temperature from 300 to 800 °C. It was found that the conductivity depended on a chemical composition of the samples and the atmosphere. Overall, the electrical conductivity was higher in wet atmospheres that contained oxygen that was in accordance with the model of a proton transport in perovskite structure which assumed the presence of the oxygen vacancies. The solid solution containing 5 mol% of calcium showed the highest conductivity and the lowest activation energy of conductivity regardless of the atmospheres; this can be attributed to the local changes in the cubic perovskite structure. Test results for CaZr0.9Y0.1O3 used as an electrolyte in solid oxide galvanic cells involving CaCr2O4 as a reference electrode are also reported.

Femtosecond laser dressing of the surfaces of porous alumina grinding wheels

The interaction of 180 fs, 775 nm laser pulses with the surfaces of alumina and glass under controlled gas atmospheres at ambient pressure has been investigated to study material redeposition, residual surface roughness and ablation rate. The effect of using various gases to protect the surface of the material appears to interfere with the effects of the plasma and can change the resulting microstructure of the dressed surface. By varying the combinations of fluence and laser scanning speed during ultra fast ablation at high repetition rates an optimum dressing condition can be reached. The process can be used to continuously dress porous vitrified cutting tools that are used for micro and nanogrinding processes.

Properties of BaCe 1− xTi xO 3 materials for hydrogen electrochemical separators

In this work the structural, microstructural and electrical properties of BaCe 1− x Ti x O 3 materials were investigated. The series of materials with different titanium concentrations x (0–0.3) were prepared by solid-state reaction method. The structural studies by X-ray diffraction have shown that undoped material crystallizes in orthorhombic phase, while the increasing concentration of Ti dopant up to x = 0.2 leads to the ordering of the structure to phases with higher symmetries (tetragonal and even cubic). The estimated solubility limit was found to be not higher than 20 at.% of Ti. Microstructure observations by scanning electron microscopy and linear contraction determination have shown the strong influence of Ti dopant on microstructure and an improvement of sinterability. The DC four-probe electrical conductivity measurements accompanied by the potentiometric EMF measurements of solid-state electrochemical cells in controlled gas atmospheres (containing H 2, O 2 and H 2O) and temperatures (500–800 °C) allowed determination of the total and partial electrical conductivities of selected materials. It was found that the introduction of Ti dopant leads to a decrease in total electrical conductivity by ca. one order of magnitude compared to the undoped material, almost independently of Ti concentration. Also, the modification of transport properties after doping with titanium was determined.

Analysis of XPS spectra of Fe 2+ and Fe 3+ ions in oxide materials

Samples of the iron oxides Fe 0.94O, Fe 3O 4, Fe 2O 3, and Fe 2SiO 4 were prepared by high temperature equilibration in controlled gas atmospheres. The samples were fractured in vacuum and high resolution XPS spectra of the fractured surfaces were measured. The peak positions and peak shape parameters of Fe 3p for Fe 2+ and Fe 3+ were derived from the Fe 3p XPS spectra of the standard samples of 2FeO·SiO 2 and Fe 2O 3, respectively. Using these parameters, the Fe 3p peaks of Fe 3O 4 and Fe 1− y O are analysed. The results indicate that high resolution XPS techniques can be used to determine the Fe 2+/Fe 3+ ratios in metal oxides. The technique has the potential for application to other transition metal oxide systems.