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The cubic perovskite BaRu[O.sub.3] has been synthesized under 18 GPa at 1,000[degrees]C. Rietveld refinement indicates that the new compound has a stretched Ru-O bond. The cubic perovskite BaRu[O.sub.3] remains metallic to 4 K and exhibits a ferromagnetic transition at [T.sub.c] = 60 K, which is significantly lower than the [T.sub.c] [approximately equal to] 160 K for SrRu[O.sub.3]. The availability of cubic perovskite BaRu[O.sub.3] not only makes it possible to map out the evolution of magnetism in the whole series of ARu[O.sub.3] (A = Ca, Sr, Ba) as a function of the ionic size of the A-site [r.sub.A], but also completes the polytypes of BaRu[O.sub.3]. Extension of the plot of [T.sub.c] versus [r.sub.A] in perovskites ARu[O.sub.3] (A = Ca, Sr, Ba) shows that [T.sub.c] does not increase as the cubic structure is approached, but has a maximum for orthorhombic SrRu[O.sub.3]. Suppressing [T.sub.c] by Ca and Ba doping in SrRu[O.sub.3] is distinguished by sharply different magnetic susceptibilities [sub.x](T) of the paramagnetic phase. This distinction has been interpreted in the context of a Griffiths' phase on the (Ca Sr)Ru[O.sub.3] side and bandwidth broadening on the (Sr,Ba)Ru[O.sub.3] side. magnetism | compounds | Ruthenate

The double perovskite Sr(sub 2)FeMoO(sub 6) is a half-metallic ferrimagnet exhibiting significant magnetoresistance (MR) at 300 K in a magnetic field H

Abstract: The performance of Nd2− x La x NiO4+ δ as a cathode material for solid oxide fuel cell (SOFC) was evaluated in this paper. Substitution of smaller Nd3+ ion for La3+ in La2NiO4+δ increased the retention of mobile interstitial oxygen defects (Oi″ ions). The concentration of the Oi″ ions in Nd2NiO4+ δ was stabilized at δ ≈0.12 at 800 °C in air after thermal cycling. As a mixed oxide-ion/electronic conductor (MIEC), Nd2NiO4+ δ gave a performance comparable to that of the best perovskite cathode material, SrCo0.8Fe0.2O3− δ (SCF), for the Sm-doped ceria (SDC) electrolyte-supported SOFC. However, the Nd2NiO4+ δ cathode exhibited a higher overpotential with La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM) as the electrolyte, presumably due to the interdiffusion of La3+ and Nd3+ ions across the electrolyte/cathode interface and subsequent formation of ion-blocking phases at the interface. La1.2Nd0.8NiO4+ δ , on the other hand, provided La isoactivity across the LSGM/cathode interface and therefore an improved performance with the LSGM electrolyte. Since Nd2− x La x NiO4+ δ contains neither Sr nor Co, as a cathode, it might be compatible with the electrolytes such as yttria-stabilized zirconia without the need of a buffer layer. [Copyright &y& Elsevier]

Abstract: For comparison with the Mn4+/Mn3+ oxoperovskites at the crossover from localized to itinerant behavior of the σ-bonding e electrons, the electronic properties of three oxygen non-stoichiometric, mixed-valent Fe4+/Fe3+ oxoperovskites were explored by measuring their resistivity ρ(T), thermoelectric power α(T), and magnetic susceptibility χ(T). Oxidation of Ca2Fe2O5 by annealing in ozone progresses by oxygen insertion to give conductive CaFeO3 perovskite clusters in a localized-electron, weakly oxidized brownmillerite Ca2Fe2O5+ δ matrix. Removal of 0.12 oxygen per formula unit from La1/3Sr2/3FeO3 lowers somewhat its cooperative disproportionation reaction, and fivefold-coordinated ions neighboring oxygen vacancies in the more ionically bonded slabs act as donors to the covalently bonded Fe(V)O6 planes. Single-crystal SrFeO2.83 exhibited bad-metal behavior with superparamagnetic, electron-rich fluctuations below 240K that, on cooling below 190K, become progressively trapped by the oxide-ion vacancies as an immobile second phase; long-range antiferromagnetic order is stabilized below a T N≈60K. [Copyright &y& Elsevier]

The temperature dependence of the paramagnetic susceptibility χm(T) taken in 2500 Oe, the resistivity ρ(T), and the thermoelectric power α(T) of DyBaCo2O5+x, which has Ba and Dy ordered into alternate (001) planes of an oxygen-deficient perovskite, have revealed a phase segregation in the compositional range 0.3x<0.5. Orthorhombic DyBaCo2O5.51 has, in addition, oxygen vacancies ordered into alternate rows of the DyO0.51 (001) planes; a cold-pressed polycrystalline sample exhibits a first-order insulator–metal transition at TIM=320 K, a Curie temperature TC=300 K, and a broadened metamagnetic transition temperature TM≉265 K in 2500 Oe. A ferromagnetic M–H hysteresis curve fails to saturate at 5 T, and a minority ferromagnetic phase below TM has a volume fraction that decreases with decreasing temperature, vanishing below 50 K. Oxygen vacancies in the DyBaCo2O5.5 phase suppress the metallic state; interstitial oxygen does not. A thermoelectric power α(T)>0 of DyBaCo2O5.51 changing continuously across TIM is interpreted to manifest a metallic minority phase crossing a percolation threshold; α(T) also provides evidence for a progressive excitation of higher-spin Co(III) with increasing temperature from below 50 K to above TIM. A previous model of the RBaCo2O5.5 phase is extended to account for the Ising spin configuration below TC, the magnetic order in the presence of higher-spin octahedral-site Co(III), and the α(T) data. [Copyright &y& Elsevier]

The morphologies of the charge carriers in the perovskite system SrFe1-xTixO3-δ are explored by transport and magnetic measurements. Oxygen vacancies are present in all samples, but they do not trap out the Fe3+ ions they introduce. The x=0.05 composition was prepared with three different values of δ. They all show small-polaron conduction above 225 K; but where there is a ratio c=Fe4+/Fe<0.5, the polaron morphology appears to change progressively with decreasing temperature below 225 K to two-Fe polarons that become ferromagnetically coupled in an applied magnetic field at lower temperatures; With an applied field of 2500 Oe, divergence of the paramagnetic susceptibility for zero-field-cooled and field-cooled samples manifests a greater stabilization of ferromagnetic pairs on cooling in the applied field. With a c>0.5, the data are consistent with a disproportionation reaction 2Fe4+=Fe3++Fe(V)O6/2 that inhibits formation of two-Fe polarons and, on lowering the temperature, creates Fe3+–Fe(V)–Fe3+ superparamagnetic clusters. [Copyright &y& Elsevier]

Studies the effect of tolerance factor and local distortion on the magnetic properties of perovskite manganites. Effects of substitutions of rare earths for La on magnetic properties; Magnetoresistance of the perovskites; Changes in perovskite structures; Differences in the ionic radii of the A-site cations on resistivity, coercivity and magnetoresistance.

You have a moon, I have a moon. We each have a weapon To be handy with, Each have a trail To follow Under this cold light. Tracks; droppings; Fur [...]

The little stones, Remember them, that Climb season to season Upward through Earth, faithful. They were not here Last year; this year They click and bounce On the plough-sock, Seed [...]

Focuses on the use of hydroxylamine hydrochloride as a reducing agent, which can be used to obtain fine particles of binary metal oxides from their respective ammonium salts. Information on an approach which can be used to reduce transition-metal oxides to aqueous solutions; Identification of transition-metal oxides.