Date of Award

8-10-2005

Degree Type

Dissertation

Degree Name

Ph.D.

Degree Program

Chemistry

Department

Chemistry

Major Professor

Wiley, John

Second Advisor

Stevens, Edwin

Third Advisor

Fang, Jiye

Fourth Advisor

Whittenburg, Scott

Fifth Advisor

Rick, Steven

Abstract

Topotactic routes have been used to produce new materials with tunable electronic and magnetic properties. The host materials were the single and triple layered Ruddlesden-Popper compounds, NaLnTiO4 (Ln = La and Gd) and A2La2Ti3O10 (A = Li and K). These compounds consist of [LnTiO4]- and [La2Ti3O10]2-, respectively, perovskite layers interleaved with two alkali metal ion strata. The topotactic routes used in this research were ion exchange and intercalation. Ion exchange was used to replace the cations in the interlayer space with a cationic unit: vanadyl or the transition metal ion, nickel. This ion exchange route opens the structure to further chemistry because each alkali metal ion is replaced by a divalent ion and a vacancy. In these vacancies other atoms can be inserted. Reductive intercalation with alkali metals is of special interest due to their propensity for forming mixed valence compounds. Mixed valency is usually correlated with semiconductive, metallic or superconductive behaviors, and unusual magnetic properties (CMR). Na0.1(VO) Na0.1(VO) 0.45LaTiO4, Na0.05(VO)0.48GdTiO4 and Li0.3Ni0.85La2Ti3O10 have been obtained by ion exchange reactions. Also, the reactivity of Na0.05(VO)0.48GdTiO4, (VO) La2Ti3O10 and Li0.3Ni0.85La2Ti3O10 is probed by an intercalation reaction with n-BuLi. Lithium insertion between the perovskite blocks reduces the titanium in the perovskite sheets and produces new mixed valence titanates. Lithium intercalation in the vanadyl compounds, Na0.05(VO)0.48GdTiO4 , as well as (VO)La2Ti3O10 gives rise to new magnetic properties. The crystal structures, thermal behavior, electronic and magnetic properties of these new compounds will be discussed.

Rights

The University of New Orleans and its agents retain the non-exclusive license to archive and make accessible this dissertation or thesis in whole or in part in all forms of media, now or hereafter known. The author retains all other ownership rights to the copyright of the thesis or dissertation.

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