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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