Synthesis, structure and properties of ternary and quaternary rare earth chalcogenides

Includes bibliographical references (pages 152-157)Solid state chemistry has seen tremendous progress in the last two decades. The impetus comes from the needs and desire for the production of novel materials in the fields of electronics, catalysis, high strength applications, optical and medical industries, etc. This dissertation looks at the development of several rare earth chalcogenides which could prove to be useful in these fields. The ternary reduced tantalate, Sr₃O₅Ta₁₅, crystallizes in the tetragonal space group P 4/m b m (No. 127) with lattice constants a = b = 12.425(4) Å, c = 3.891(2) Å. This reduced oxide can exist since the states below the Fermi level are mainly comprised of metal-oxygen nonbonding character. This tantalate also exhibits superconductive characteristics at T[sub c] ≈ 7 K. Quaternary reduced oxides were also studied, with an emphasis on the K₉Ta₁₄Si₄O₄₇ system which crystallizes in the hexagonal space group P 6₃/m c m (No. 193) with lattice constants a = b = 9.0533(4) Å, c = 27.901(2) Å. Quinary reduced oxides are especially difficult to synthesize. We managed to make and study La₃CoWO₆S₃ which has a structure related to the common perovskite structure used for magnetic materials.Ph.D. (Doctor of Philosophy