Activities of FexO in Na2O-Al2O3-SiO2-FexO Homogeneous Liquid Slags at 1673 K

Electrochemical measurements of the solid-oxide galvanic cell of the type Mo/Mo + MoO[2]/ZrO[2] (MgO)/Fe + {Na[2]O-Al[2]O[3]-SiO[2]-FexO} slag/Ag/Fe were conducted at 1673 K in order to obtain the activities of FexO in Na[2]O-Al[2]O[3]-SiO[2]-FexO system. The iso-activity curves for FexO at 1673 K were determined for Na[2]O-(Al[2]O[3] + SiO[2])-FexO pseudo-ternary slags with an Al[2]O[3]/SiO[2] molar ratio of 33/67

Sulphur potential measurements with a two-phase sulphideoxide electrolyte

The open circuit potentials of the galvanic cell,Pt (or Au)|(Ar + H2S + H2)'||CaS + ZrO2(CaO)|| (Ar + H2S+ H2)"|Pt (or Au) has been measured in the temperature range 1000 to 1660 K and PH2S:PH 2 ratios from 1.73×10-5 to 2.65×10-1. The solid electrolyte consists of a dispersion of calcium sulphide in a matrix of calcia-stabilized zirconia. The surface of the electrolyte is coated with a thin layer of calcium sulphide to prevent the formation of water vapour by reaction of hydrogen sulphide with calcium oxide or zirconia present in the electrolyte. The use of a point electrode with a catalytically active tip was necessary to obtain steady emfs. At low temperatures and high sulphur potentials the emfs agreed with the Nernst equation. Deviations were observed at high temperatures and low sulphur potentials, probably due to the onset of significant electronic conduction in the oxide matrix of the electrolyte. The values of oxygen and sulphur potentials at which the electronic conductivity is equal to ionic conductivity in the two-phase electrolyte have been evaluated from the emf response of the cell. The sulphide-oxide electrolyte is unsuitable for sulphur potential measurements in atmospheres with high oxygen potentials, where oxidation of calcium sulphide may be expected

Exact dimer ground state of the two dimensional Heisenberg spin system SrCu_2(BO_3)_2

The two dimensional Heisenberg model for SrCu_2(BO_3)_2 has the exact dimer ground state which was proven by Shastry and Sutherland almost twenty years ago. The critical value of the quantum phase transition from the dimer state to the N\'{e}el ordered state is determined. Analysis of the experimental data shows that SrCu_2(BO_3)_2 has the dimer ground state but is close to the transition point, which leads to the unusual temperature dependence of the susceptibility. Almost localized nature of the triplet excitations explains the plateaus observed in the magnetization curve.Comment: 4 pages, 5 figures, to appear in PR

Quantum Monte Carlo Simulation of the Trellis Lattice Heisenberg Model for SrCu2_2O3_3 and CaV2_2O5_5

We study the spin-1/2 trellis lattice Heisenberg model, a coupled spin ladder system, both by perturbation around the dimer limit and by quantum Monte Carlo simulations. We discuss the influence of the inter-ladder coupling on the spin gap and the dispersion, and present results for the temperature dependence of the uniform susceptibility. The latter was found to be parameterized well by a mean-field type scaling ansatz. Finally we discuss fits of experimental measurements on SrCu$_2$O$_3$ and CaV$_2$O$_5$ to our results.Comment: 7 pages, 8 figure