Europium titanate has the cubic perovskite structure containing divalent Eu (7 μB) and tetravalent Ti. From magnetic measurements we find that EuTiO3 is one of the few antiferromagnetic materials with a positive θ (TN=5.3°K, θ=3.8°K). At 1.3°K the magnetic moment (σ) increases linearly with field to 10 kOe; above 14 kOe the moment saturates and σ=156 emu/gm (6.93 μB) at 20 kOe. Powder neutron-diffraction work indicates that EuTiO3 has the Type G magnetic structure in which a given Eu++ has six nearest-neighbor europium ions antiparallel and 12 next-nearest-neighbor europium ions parallel. In a perovskite structure where only the 12-coordinated ion is magnetic, i.e., Eu++, the molecular field relations for a two sublattice model yield J1/k=−0.021°K, where J1 is the effective intersublattice exchange interaction, and J2/k=0.040°K, where J2 is the effective intrasublattice exchange interaction. The signs of J1 and J2 are opposite to those found in the europium chalcogenide series. The chalcogenides, however, have the rocksalt structure in which the number of 90° cation-anion-cation interactions differs from the perovskite structure.

The supercooling and freezing of a restricted liquid has been studied by the probing of its molecular dynamics with picosecond optical techniques. A newly developed transparent porous host material makes it possible to study the liquid viscosity as a function of the confining pore radius and temperature. The observed behavior is remarkably different from that of an ordinary liquid, and can be interpreted in terms of a simple model. PACS numbers: 64.70.Dv, 61.25.Em, 62.10.+$, It is well known that the properties of liquids can be modified by their confinement in very small pores. Experiments on helium in Vycor glass^ and on other confined liquids^ have revealed a variety of phenomena whose interpretation has often been difficult and frequently controversial. One example concerns the observed freezing-point depression of liquids in porous media, where it is still not clear whether the depression is a result of a finite-size-related shifting of the phase diagram or, in fact, a consequence of genuine supercooling below the normal freezing point. More generally, although a certain amount of progress has been made in recent years, ^'"^ there is not universal agreement on many fundamental issues concerning the phase transitions of a restricted liquid. We report here on a series of time-resolved optical experiments to study the dynamics of liquid oxygen in small pores. The use of a novel porous host material allowed a systematic investigation of liquid confinement effects as a function of pore size, thereby shedding new light on the properties of supercooled restricted liquid and the way it freezes. A simple model is presented which offers a qualitative interpretation of the experimental results.Well-characterized porous sol-gel glasses^ of good optical quality and moderate mechanical strength were used to confine the liquid. The most important features of the glasses include their high porosity ( ~ 70%) and a well-defined pore size and aspect ratio as characterized by mercury porosimetry, vaporpressure isotherms, and stereo transmission-electronmicroscope images. The pore size can be controlled in the fabrication process to provide a pore radius ranging from '-^ 10 to 250 A. The glasses were mounted in a copper and brass optical cell, which was then placed inside a variable-temperature optical cryostat. A small amount of helium gas was added to ensure thermal equilibrium of the porous glass with the surrounding cell, yielding a temperature stability of ±0.005 K. Research-grade oxygen gas was added carefully in measured doses until the pores were completely filled with the physisorbed liquid.A subpicosecond optical technique was used to study the dynamical properties of the restricted liquid as it was cooled below the ordinary bulk freezing point. Optical pulses of 500-fs duration at a 76-MHz repetition rate were obtained from a dual-jet dye laser, synchronously pumped by a mode-locked argon-ion laser. The dye-laser wavelength was set at 584 nm, far enough from the oxygen bimolecular absorption line at 577 nm to avoid an...

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A high-water-pressure high-temperature study has been conducted of the systems Y2O3-H2O, Smz03-Hz0, Ndr03-Hz0, and Laz03-H20. The trihydroxides La(OH)3, Nd(OH)r, and Sm(OH)3 are isomorphous, but Y(OH)a does not belong to this group. On the other hand, the oxyhydroxides YOOH, SmOOH, and NdOOH are isomorphous; LaOOH, if it exists, cannot be stable in the presence of water at room temperature. Pressuretemperature curves for the equilibrium between the trihydroxide, oxyhydroxide, and a new hydroxy compound have been determined for each of the three smaller ions. The reversibility of the transition between the A-, B-, and C-type rare earths has been established, and new X-ray data on the B structure are listed. The relations between the polymorphs as a function of ionic size are changed from those given by Goldschmidt. The very marked difference in stability in air between the A-and C-type structxires suggests the obvious desirability of converting rare-earth oxide ceramics into the C structure with proper compositional variation and thermal treatment.

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Six transition metal dioxides, M002, WO2, ReO2, auO2, OsO2, and IrO2, have been examined as electrodes in H2SO4 solution. The oxides M002, WO2, ReO2, and RuO2 have broad current-potential profiles, indicating the formation of a surface layer which can exist over a range of compositions. Steady-state measurements of 02 reduction showed catalytic activities which were low compared to common 02 catalysts such as Pt, but of the same order as other oxide catalysts. Activities were lowest for WOe and ReO2, which form resistive surface layers of a higher oxide. The only material studied which was sufficiently stable to allow measurement of both 02 evolution and O2 reduction was RuO2. The current-potential profiles of OsO2 and IrO2 are characterized by distinct changes of oxidation state. These two oxides were not sufficiently stable to allow the measurement of 02 reduction. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 35.8.191.249 Downloaded on 2015-02-09 to IP Vol. 124, No. 8 METAL DIOXIDES 1203 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 35.8.191.249 Downloaded on 2015-02-09 to IP Vol. I24, No. 8 * Electrochemical Society Active Member, Key words: lithium-silicon electrode, high specific capacity, high current density, molten salt battery. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 35.8.191.249 Downloaded on 2015-02-09 to IP

Daniel has used an expression similar to Eq. (8) to compute the impurity resistivities of Cuand Au-based alloys containing transition-metal impurities. 5