MAIN-GROUP ELEMENT SIZE AND SUBSTITUTION EFFECTS ON THE STRUCTURAL DIMENSIONALITY OF ZIRCONIUM TELLURIDES OF THE ZRSIS TYPE

Chemical and structural variations in compounds related to the layered compound ZrSiTe have been examined. A study of ZrSi1-xGexTe solid sol utions show that the Si:Ge ratio can be varied in any stoichiometric p roportion with the result that increasing atomic size (increasing x) a ffects both the shrinkage of the c axis and the expansion of the a axi s. Expansion of the a axis results in relief of steric crowding within and between Te layers that permits increased bonding between Zr and T e in adjacent layers, This steric-electronic synergy is discussed, A n ew member of this structural family, ZnSnTe, was synthesized (space gr oup P4/nmm, No, 129, Z = 2, a = 4.0549(6) Angstrom, c = 8.711(2) Angst rom). ZrSnTe has a fully three-dimensional structure; bond distances o f Zr to the intralayer and interlayer Te, 3.038 and 3.084 Angstrom, re spectively, are almost equal, Four new pseudoternary tellurides are re ported. Two of pseudoternary tellurides, ZrSi0.66As0.34Te and ZrSi0.5A s0.7Te0.8, were refined in the same space group with lattice parameter s a = 3.8116(1) Angstrom, c = 8.398(3) Angstrom for ZrSi0.5As0.7Te0.8 and a = 3.7110(3) Angstrom, c = 9.723(2) Angstrom for ZrSi0.66As0.34Te ZrSi0.66As0.34Te, isostructural with ZrSiTe, has a c axis length 0.22 Angstrom larger than that of ZrSiTe; arsenic in this material substit utes solely for silicon, The isotypic ZrSi0.5As0.7Te0.8 exhibits subst itution for both Si and Te and can be formulated as Zr(Si0.5As0.5)(As0 .2Te0.8). Four-probe resistivity measurements (77-300 K) show all tern ary and pseudoternary tellurides to be metallic with resistivities of similar to 10(-4) Omega cm.