SYNTHESIS, CRYSTAL-STRUCTURE, RAMAN-SPECTROSCOPY, AND PHYSICAL CHARACTERIZATION OF A NEW COBALT PHOSPHO-SILICIDE COSI3P3

New phospho-silicide CoSi3P3 has been synthesized and its crystal stru cture determined by single crystal X-ray diffraction (R = 0.035, R(W) = 0.032). CoSi3P3 (Z = 4) crystallizes with the pseudo-orthorhombic sy mmetry and meriedric twinning in the space group P2(1). Lattice parame ters are a = 5.899(1) Angstrom, b = 5.703(1) Angstrom, c = 12.736(1) A ngstrom, beta = 90 degrees. The crystal structure can be described by zigzag chains of octahedra occupied by Co atoms alternating with zigza g chains of tetrahedra occupied by P or Si atoms. Single crystals of t his phase have be en investigated at room temperature by polarized Ram an spectroscopy in the 100-600 cm(-1) range. The results confirm the m onoclinic symmetry of COSi3P3. Magnetic susceptibility and electronic conductivity have been measured between 300 and 10 K. CoSi3P3 is diama gnetic at room temperature and paramagnetic below 65 K. CoSi3P3 is sem iconducting at room temperature with an energy gap of about 0.12 eV. ( C) 1996 Academic Press, Inc.