Interaction of lanthanum or cerium with nickel and arsenic: phase diagramsand structural chemistry

Solid-state phase equilibria in the ternary La-Ni-As and Ce-Ni-As phase dia grams have been established using X-ray diffraction, scanning electron micr oscopy and electron probe microanalysis. The lanthanoid-poor region up to 3 3 at.% Ln was investigated at 1070 K, whereas the Ln-rich corner, due to th e generally lower melting points, was investigated at 870 K. Seven ternary arsenides with cerium and six ternary compounds with lanthanum were found. Most were characterized structurally, either by powder or single crystal te chniques. Based upon these results, three new series of ternary lanthanoid- nickel arsenides were synthesized: LnNiAs (YbPtP type) (Ln: La-->Tm), Ln(20 )Ni(42)As(31) (Sm20Ni42P31 type) (Ln: La-->Dy, Y) and Ln(6)Ni(13.4)As(9) (B aAl4-type derivative) (Ln=La, Ce, Nd). The lattice parameters of these new compounds were refined using powder diffraction data. (C) 1999 Elsevier Sci ence S.A. All rights reserved.