SYNTHESIS, STRUCTURE, AND MAGNETIC-PROPERTIES OF THE NEW TERNARY NITRIDE BAHFN2 AND OF THE BAHF1-XZRXN2 SOLID-SOLUTION

The new ternary nitrides BaHf1-xZrxN2 (0 less than or equal to x less than or equal to 1) have been synthesized by the solid state reaction of the binary nitrides Ba3N2, Hfn, and ZrN and characterized by powder X-ray diffraction. The crystal structure of the end member, BaHfN2, h as been refined from powder data. The nitridohafnate crystallizes in t he tetragonal space group P4/nmm (a = 4.1279(1) Angstrom, c = 8.3816(4 )Angstrom, Z = 2) and is isostructural with the oxide KCoO2. Hafnium i s coordinated to five nitrogens in a distorted square base pyramidal g eometry, forming layers of edge-sharing pyramids which stack along the c axis. Barium is situated between the Hf-N layers and is coordinated to five nitrogen atoms. Samples exhibit temperature-dependent paramag netism between approximately 8 and 293 K and become superconducting be low 8 K. (C) 1998 Academic Press.