SYNTHESIS AND STRUCTURE OF 2 NEW LAYERED TERNARY NITRIDES, SRZRN2 ANDSRHFN2

The new ternary nitrides SrZrN2 and SrHfN2 have been synthesized by th e solid state reactions of Sr2N with ZrN and HfN and characterized by powder X-ray diffraction. Both nitrides form structures in the hexagon al space group R(3) over barm$ (SrZrN2, a = 3.37302(5) Angstrom, c = 1 7.6756(3) Angstrom, Z = 3; SrHfN2, a = 3.34481(3) Angstrom, c = 17.677 9(2) Angstrom , z = 3) and are isostructural with alpha-NaFeO2. The st ructures are constructed of alternating layers of strontium-nitrogen e dge-sharing octahedra and either zirconium-nitrogen or hafnium-nitroge n edge-sharing octahedra stacked along the c axis. Alternatively, Sr2 can be regarded as occupying octahedral holes between Zr(Hf)N-2 octah edral layers. The title nitrides are essentially diamagnetic at room t emperature, consistent with the chemical composition. These compounds are the first alkaline earth ternary nitrides observed to have the alp ha-NaFeO2 layered structure.