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Results indicate that zirconium and hafnium nitride halides crystallize into hexagonal shapes and with lithium intercalation they are transformed to solvent free superconductors. Data further show that the electronic structures of the crystals vary.

Pauling's second crystal rule is used to predict the distribution of anions in mixed oxyanion systems such as oxynitrides and oxyhalides with diverse compositions and structure types. The results are presented in a plot correlating the charge of the anions obtained from the observed occupancies in crystallographic positions with the calculated bond strength sums for these sites.

Research has been conducted on the superconducting compounds which contain transition metals other than copper. The synthesis and structural characterization of the (SrO)(SrNbO (sub)2-x N) (sub)n (n= 1,2) has been carried out and the results indicate that these compounds constitute Ruddlesden-Popper strontium niobium oxynitrides and provide layered parent structures.

Non‐centrosymmetric polar compounds have important technological properties. Reported perovskite oxynitrides show centrosymmetric structures, and for some of them high permittivities have been observed and ascribed to local dipoles induced by partial order of nitride and oxide. Reported here is the first hexagonal perovskite oxynitride BaWON2, which shows a polar 6H polytype. Synchrotron X‐ray and neutron powder diffraction, and annular bright‐field in scanning transmission electron microscopy indicate that it crystalizes in the non‐centrosymmetric space group P63mc, with a total order of nitride and oxide at two distinct coordination environments in cubic and hexagonal packed BaX3 layers. A synergetic second‐order Jahn–Teller effect, supported by first principle calculations, anion order, and electrostatic repulsions between W6+ cations, induce large distortions at two inequivalent face‐sharing octahedra that lead to long‐range ordered dipoles and spontaneous polarization along the c axis. The new oxynitride is a semiconductor with a band gap of 1.1 eV and a large permittivity. [ABSTRACT FROM AUTHOR]

Non‐centrosymmetric polar compounds have important technological properties. Reported perovskite oxynitrides show centrosymmetric structures, and for some of them high permittivities have been observed and ascribed to local dipoles induced by partial order of nitride and oxide. Reported here is the first hexagonal perovskite oxynitride BaWON2, which shows a polar 6H polytype. Synchrotron X‐ray and neutron powder diffraction, and annular bright‐field in scanning transmission electron microscopy indicate that it crystalizes in the non‐centrosymmetric space group P63mc, with a total order of nitride and oxide at two distinct coordination environments in cubic and hexagonal packed BaX3 layers. A synergetic second‐order Jahn–Teller effect, supported by first principle calculations, anion order, and electrostatic repulsions between W6+ cations, induce large distortions at two inequivalent face‐sharing octahedra that lead to long‐range ordered dipoles and spontaneous polarization along the c axis. The new oxynitride is a semiconductor with a band gap of 1.1 eV and a large permittivity. [ABSTRACT FROM AUTHOR]

Electronic flexibility and colossal magnetoresistance effects are discovered in the perovskite oxynitrides EuW[O.sub.1+x][N.sub.2-x] and ammonolysis of [Eu.sub.2][W.sub.2][O.sub.9] has produced scheelite-type intermediates EuW[O.sub.4-y][N.sub.y] with a small degree of nitride substitution. Both the Eu and W oxidation states and the hole/electron doping are tuned by varying the O/N ratio, EuW[O.sub.1+x][N.sub.2-x] phases order ferromagnetically at 12 K and colossal magnetoresistances (CMR) are seen in the least doped sample.

The perovskite oxynitrides EuM[O.sub.2]N (M = Nb, Ta) are prepared and their coupled colossal magneto-resistive and capacitive effects are studied. The results have shown an excellent potential for large magneto-responses in materials like EuNb[O.sub.2]N, which has combined the large [Eu.sup.2+] spin and the off-center instability of [Nb.sup.5+] enhanced by bonding to nitride.

Rietveld method was used to refine the crystal structure of the n = 1 member of the Ruddlesden-Popper family (SrO)(SrNbO2N)n. The refined stoichiometry obtained by neutron diffraction for the n = 1 compound is Sr2-NbO3.28N0.72, indicating that a mixed-valence state for niobium, intermediate between +4 and +5 that results from a nitrogen deficiency with respect to the nominal stoichiometry.

The topotactic nitridation of cation ordered, tetragonal Sr2FeMoO6 in NH3 at moderate temperatures leads to cubic, Fm3̅m double perovskite oxynitride Sr2FeMoO4.9N1.1 where double-exchange interactions determine ferromagnetic order with TC≈ 100 K. Substitution of oxide by nitride induces bond asymmetries and local electronically driven structural distortions, which combined with Fermi level lowering restricts charge itinerancy to confined regions and preclude spontaneous long-range magnetic order. Under a magnetic field, ferromagnetic correlations expand, favoring charge delocalization and a negative magnetoresistance is observed. [ABSTRACT FROM AUTHOR]