Development of improved p-type Si-20 at. % Ge by addition of fullerite

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:46458

Cook, B A; Harringa, J L

In a series of experiments designed to evaluate the possibility of lowering the lattice thermal conductivity of silicon-germanium alloys through the formation of an inert, intragrannular nanophase, a number of p-type Si-20 at. % Ge alloys, with a nominal doping level of 0.5 at. % boron, were prepared with varying amounts of fullerite, a mixture of 90% C{sub 60} + 10% C{sub 70} with a particle size of 0.7 nm. The alloys were synthesized by mechanical alloying (MA) and the fullerite was added at various stages of the preparation sequence. Compacts consolidated by hot pressing at temperatures of 1200 to 1265 C were found to be fully dense and homogeneous. Each compact was characterized by Hall effect at room temperature and also by electrical resistivity, Seebeck coefficient, and thermal diffusivity measurements to 1000 C. A reduction in thermal conductivity of up to 22% compared to standard p-type alloys was observed in samples containing 0.8 wt % additions. In this study, a maximum integrated average figure of merit, Z, between 300 and 1000 C of 0.65 {times} 10{sup {minus}3} {degree}C{sup {minus}1} was obtained, corresponding to 0.4 wt % addition of fullerite. Observation of selected samples by transmission electron microscopy revealed that the fullerite reacted with silicon to form nanophase SiC inclusions.

• Research Organization: Ames Lab., IA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 46458
• Report Number(s): IS-M--811; CONF-940830--3; ON: DE95010230
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
36 MATERIALS SCIENCE
BORON ADDITIONS
FULLERENES
GERMANIUM ALLOYS
PHYSICAL PROPERTIES
SILICON ALLOYS
THERMAL CONDUCTIVITY
THERMOELECTRIC MATERIALS
THERMOELECTRIC PROPERTIES