Degree Type

Dissertation

Date of Award

1992

Degree Name

Doctor of Philosophy

Department

Chemistry

First Advisor

John D. Corbett

Abstract

Syntheses of both binary M[subscript]5X[subscript]3 hosts and M[subscript]5X[subscript]3Z interstitial compounds with the same Mn[subscript]5Si[subscript]3 structure type was extended to rare-earth metal tetrelides. The variety of interstitials Z that were incorporated into these host binaries allowed the modulation of the bonding and properties of the host compound without greatly altering or breaking up the structure. Investigations on the binaries also revealed that both La[subscript]5Ge[subscript]3 and La[subscript]5Pb[subscript]3 exist in the Mn[subscript]5Si[subscript]3-type, and La[subscript]5Sn[subscript]3 exists only in the W[subscript]5Si[subscript]3-type contrary to previous reports. Exploratory work on La[subscript]5Ge[subscript]3Z, La[subscript]5Pb[subscript]3Z, and La[subscript]5Sn[subscript]3Z resulted in the synthesis of more than 30 new interstitial compounds with structures related to the filled-Mn[subscript]5Si[subscript]3 and Cr[subscript]5B[subscript]3 structure types. The novel transition-metal-stabilized analogs Ca[subscript]5Pb[subscript]3Z were also synthesized and characterized. Based on XPS, results these compounds contain "cationic" interstitials in contrast to the La[subscript]5Ge[subscript]3Z and La[subscript]5Pb[subscript]3Z phases. Application of the Zintl concept to the bonding interpretation of these compounds was fairly successful;Although a large number of interstitial compounds having the filled-Mn[subscript]5Si[subscript]3 structure are known, ordered but partially filled examples have not been reported. A new class of compounds La[subscript]15Ge[subscript]9Z (Z = Mn-Cu, P, C, O) with a hexagonal √3 x √3 superstructure of the Mn[subscript]5Si[subscript]3 structure type was synthesized and characterized. Structural investigations also revealed that Ca[subscript]5.67Pb[subscript]3 had a related √3 x √3 superstructure with calcium atoms occupying two-thirds of the interstitial sites in an ordered manner. Physical property measurements and band structure calculations indicated that it was a semiconductor. The apparent electron-deficiency was resolved by the formation of Pb-Pb dimers;The compounds La[subscript]5Ge[subscript]3Z (Z = group 13 and 14 elements) were found to contain dimers in structures related to Zr[subscript]5Si[subscript]4, Sm[subscript]5Ge[subscript]4 and Gd[subscript]5Si[subscript]4 types. The structural relationships between the various 5:4 structures were discussed. Similarly, a novel compound RE[subscript]5Ru[subscript]2 (RE = La, Nd) was synthesized and characterized. The structure contains chains of Ru-centered edge-sharing La octahedra similar to those found in Pr[subscript]4I[subscript]5Ru. RE[subscript]5RuGe[subscript]2 (RE = La, Nd) become antiferromagnetic around 45°K;Physical property measurements, XPS experiments and extended-Huckel calculations on selected compounds provided information on the nature of their chemical bonding. ftn*DOE Report IS-T-1573. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy.

DOI

https://doi.org/10.31274/rtd-180813-11827

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Arnold Mejia Guloy

Language

en

Proquest ID

AAI9220970

File Format

application/pdf

File Size

396 pages

Share

COinS