Rare-earth compounds with the Th₃P₄-type structure

Th3P4-type compounds occur in rare-earth systems with elements of Vth and VIth group of the periodic system. In general, the existence of Th3P4 compounds appears to be coupled with the formation of 1:1 compounds of the NaCl type in the same system. Analysis of I 4̄ 3d symmetry reveals certain similarities of atomic coordination and distances in both structures. In RE3-xvxX4 (X=S, Se, Te) (0≦x≦1/3) the rare-earth ions occupy a defect Th3 lattice with a random vacancy distribution. With increasing vacancy concentration x, the materials change continuously from metals to insulators and interesting electrical, ferromagnetic, or superconducting properties have been observed. The Vth group elements, Sb and Bi, form metallic compounds without a homogeneity range and with the rare-earth ions on the P4 sites. © 1966 The American Institute of Physics.