Synthesis and Structure Determination of the Quaternary Zinc Nitride Halides Zn2NX1−yX′y (X, X′ = Cl, Br, I; 0 < y < 1)
The quaternary series Zn2NCl1−yBry and Zn2NBr1−yIy were synthesized from solid-liquid reactions between zinc nitride and the respective zinc halides in closed ampoules, and the evolution of their crystal structures was investigated by single-crystal and powder X-ray diffraction. Zn2NX1−yX′y (X, X′ = Cl, Br, I) adopts the anti-β-NaFeO2 motif in which each nitride ion is tetrahedrally coordinated by four zinc cations, and the halide anions are located in the voids of the skeleton formed by corner-sharing [NZn4] tetrahedra. While Zn2NCl1−yBry crystallizes in the acentric orthorhombic space group Pna21 (No. 33), isotypic to Zn2NX (X = Cl, Br), the structure of Zn2NBr1−yIy is a function of the iodide concentration, namely, Zn2NBr (Pna21) for low iodine content and Zn2NI (Pnma) for higher (y ≥ 0.38).
Symmetry relations in wurtzite nitrides and oxide nitrides and the curious case of Pmc21
Binary and multinary nitrides in a wurtzitic arrangement are very interesting semiconductor materials. The group–subgroup relationship between the different structural types is established.
Visible and Ultraviolet Absorption Spectra of Nickel Chloride Dissolved in Fused LiCl–KCl Mixtures
Absorption spectra were measured for solutions of NiCl2 in fused LiCl--KCl mixtures near the eutectic composition over the wave length range of 220 to 750 m mu and at temperatures of 360 to 550 deg . In the ultraviolet region an absorption band was found with maximum at 260 m mu and a molar absorbancy index of (3.6 plus or minus 0.2) x 103 at 395 deg . The visible spectrum consisted of four overlapping bands with maxima at 512, ca. 590, 625, and 695 m mu at 398 deg . The highest of these bands (625 m mu ) had a molar absorbancy index of 61 plus or minus 3 at a temperature of 398 deg and a solvent salt composition of 41.0 mole% KCl. The absorbancy indices of all bands changed considerably with temperature. Furthermore, the ultraviolet band broadened and its maximum shifted to longer wave lengths with increasing temperature. It was shown that these absorption bands were caused by at least two light-absorbing species derived from NiCl2. With increasing temperature the concentration of one species decreased while the concentration of another species increased. At a constant temperature the concentration of all species giving rise to observed lightmore » absorption was proportional to the concentration of total nickel. The spectra were changed by a small but measurable amount with small changes in the composition of the solvent salt.« less