Graduation Year

2010

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Physics

Major Professor

George S. Nolas, Ph.D.

Co-Major Professor

Lilia Woods, Ph.D.

Committee Member

Martin Muñoz, Ph.D.

Keywords

single crystal, transport properties, silicon, thermoelectrics, Seebeck

Abstract

Intermetallic clathrates have long been of interest for materials science research.

The promise these materials hold for useful applications ranges from thermoelectrics to

photovoltaics and optoelectronics to potentially ultra-hard materials and magnetic cooling

applications. Their unique physical properties are intimately related to their intriguing

structural properties. Thus a fundamental understanding of the chemistry and physics of

inorganic clathrates offers the possibility to assess their potential for use in the various

applications mentioned above.

The purpose of the current work is to expand the current knowledge of the

synthetic routes for obtaining clathrate materials, their structural, chemical, and physical

properties, particularly those that from in the type I, II and VIII crystal structures. New

synthesis routes are presented and used for preparation of single crystals of Na 8Si46 and

Na 24Si136. Single-crystal X-ray analysis, and resistivity, Seebeck coefficient and thermal

conductivity measurements are presented. In addition, two "inverse" clathrates with

compositions Sn 24P19.3Br8 and Sn17Zn7P22Br8 have been characterized in terms of their

transport properties. Since the magnetic refrigeration based on the magnetocaloric effect

is a topic of great interest, type VIII Eu 8Ga16Ge30 clathrates are also explored in terms of

their application for magnetic cooling.

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