ABSTRACT:The alkaline earth nitridogallate Ba 3 Ga 3 N 5 was synthesized from the elements in a sodium flux at 760°C utilizing weld shut tantalum ampules. The crystal structure was solved and refined on the basis of single-crystal X-ray diffraction data. Ba 3 Ga 3 N 5 (space group C2/c (No. 15), a = 16.801(3), b = 8.3301(2), c = 11.623(2) Å, β = 109.92(3)°, Z = 8) contains a hitherto unknown structural motif in nitridogallates, namely, infinite strands made up of GaN 4 tetrahedra, each sharing two edges and at least one corner with neighboring GaN 4 units. There are three Ba 2+ sites with coordination numbers six or eight, respectively, and one Ba 2+ position exhibiting a low coordination number 4 corresponding to a distorted tetrahedron. Eu 2+ -doped samples show red luminescence when excited by UV irradiation at room temperature. Luminescence investigations revealed a maximum emission intensity at 638 nm (FWHM =2123 cm ). Ba 3 Ga 3 N 5 is the first nitridogallate for which parity allowed broadband emission due to Eu 2+ -doping has been found. The electronic structure of both Ba 3 Ga 3 N 5 as well as isoelectronic but not isostructural Sr 3 Ga 3 N 5 was investigated by DFT methods. The calculations revealed a band gap of 1.53 eV for Sr 3 Ga 3 N 5 and 1.46 eV for Ba 3 Ga 3 N 5 .

TIN-STEEL COUPLE IN AIR-FREE SOLUTION 491anodic effects. The corroding potential thus serves to give a direct indication of the corrosion rate. Unfortunately, it must be cautioned that this relationship cannot be generally extended to corrosion relationships in fruits or fruit juices. ACKNOWLEDGMENTResults presented in this paper were obtained in connection with a project on the corrosion of tin plate sponsored by the Inland Steel Co. The author wishes to thank this organization, and in particular Dr. E. D. Martin, for their support and for permitting publication of these results. He further wishes to acknowledge the help of Dr.

Abstract. The iron arsenide oxides Sr 2 CrO 3 FeAs and Ba 2 ScO 3 FeAs were synthesized by high temperature solid state reactions and their crystal structures determined by the X-ray powder diffraction. Their structures are tetragonal (P4/nmm; Sr 2 CrO 3 FeAs: a = 391.12(1) pm, c = 1579.05(3) pm; Ba 2 ScO 3 FeAs: a = 412.66(5) pm, c = 1680.0(2) pm, Z = 2) and isotypic to Sr 2 GaO 3 CuS. Iron arsenide layers are sandwiched between perowskite-like metal oxide layers and separated by ~1600 pm, which is much larger compared to the ZrCuSiAs-type '1111' iron arsenide superconductors. The bond lengths and angles within the FeAs layers are adapted to the space requirements of the oxide blocks. Measurements of the magnetic susceptibility, electrical resistivity and temperature-dependent crystal structure show no hint for a structural phase transition or magnetic anomaly in both compounds. Sr 2 CrO 3 FeAs shows Curie-Weiss paramagnetism above 160 K with an effective magnetic moment of 3.83(3) µ B in good agreement with the theoretical value of 3.87 µ B for Cr 3+ (S = 3/2).

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The symmetry requirement and the origin of magnetic orders coexisting with superconductivity have been strongly debated issues of iron-based superconductors (FeSCs). Observation of C 4 -symmetric antiferromagnetism in violation of the inter-band nesting condition of spin-density waves in superconducting ground state will require significant change in our understanding of the mechanism of FeSC. The superconducting material Sr 2 VO 3 FeAs, a bulk version of monolayer FeSC in contact with a perovskite layer with its magnetism (T N ~ 50 K) and superconductivity (T c ~ 37 K) coexisting at parent state, has no reported structural orthorhombic distortion and thus makes a perfect system to look for theoretically expected C 4 magnetisms 1-3 . Based on variable temperature spin-polarized scanning tunneling microscopy (SPSTM) with newly discovered imaging mechanism that removes the static surface reconstruction (SR) pattern by fluctuating it rapidly with spin-polarized tunneling current, we could visualize underlying C 4 symmetric (2 2) magnetic domains and its phase domain walls. We find that this magnetic order is perfectly consistent with the plaquette antiferromagnetic order in tetragonal Fe spin lattice expected from theories based on the Heisenberg exchange interaction of local Fe moments and the quantum order by disorder 4 . The inconsistency of its modulation Q vectors from the nesting condition also implies that the nesting-based C 2 symmetric magnetism is not a unique prerequisite of high-T c FeSC. Furthermore, the plaquette antiferromagnetic domain wall dynamics under the influence of small spin torque effect of spin-polarized tunneling current are shown to be consistent with theoretical simulation based on the extended Landau-Lifshitz-Gilbert equation.

A study of the solid solution of TiO2, Fe2O3, and Cr203 in mullite was made by measuring the changes in lattice parameters and unit‐cell volume. Synthetic mullite (3O3‐2SiO2) was reacted with up to 12 weight % of the oxides at temperatures ranging from 1000° to 17000C. The approximate minimum temperature required for the formation of solid solution was 12000C. for Fe203 and 1400°C. for Cr2O3 and TiO3. The maximum amount of solid solution found was 2 to 4% TiO2 at 1600°C., 10 to 12% Fe2Os at 1300°C., and 8 to 10% CrZO3 at 1600OC. Lattice parameters and unit‐cell volumes for each solid solution series increased with increasing amounts of foreign oxide. There was good agreement between the calculated and observed increase in cell dimensions for the iron oxide series. Except in the case of titania, there was good agreement between X‐ray data and petrographic observations.

The iron arsenide Sr2CrO3FeAs with the tetragonal Sr2GaO3CuS-type structure was synthesized and its crystal structure re-determined by neutron powder diffraction. In contrast to previous X-ray crystallographic studies, a mixed occupancy of chromium and iron was found within the FeAs 4/4 layer (93 ± 1%Fe : 7 ± 1%Cr). We suggest that the partial Cr-doping at the Fe site is the reason for the absence of a spin-density-wave anomaly and superconductivity in this compound. Additional experiments via neutron polarization analysis revealed short-range spin correlations below ∼100 K and long-range antiferromagnetic ordering below TN = 36 K with a magnetic propagation vector of q = ( 1 2 , 1 2 , 0). The Cr 3+ -ions form a collinear magnetic structure of the C-type in the magnetic space group CP mma (a = a − b, b = a + b, c = c), where Cr 3+ions occupy the 4g (0, 1 4 , z) Wyckoff position. The magnetic moments are aligned along the orthorhombic a -axis. At 3.5 K, an ordered magnetic moment of 2.75 ± 0.05 µB for the Cr 3+sublattice was refined.This paper is dedicated to Dr Klaus Römer on the occasion of his 70th birthday.

CuPN2 was successfully synthesized from Cu3N and P3N5 at 5 GPa and 1000 °C by employing the Walker‐type multianvil technique. Its crystal structure was elucidated from powder X‐ray diffraction data. CuPN2 is isostructural to LiPN2 and NaPN2 [tetragonal I$\bar {4}$2d, no. 122, a = 4.5029(2) Å, c = 7.6157(2) Å, V = 154.42(1) Å3, Rp = 1.303, wRp = 1.741] with a structure that can be derived from both chalcopyrite and zincblende type. The electronic structure of CuPN2 was investigated by means of DFT calculations. CuPN2 is an indirect semiconductor with a bandgap of 1.67 eV.