Miniaturized Radioisotope Solid State Power Sources
Electrical power requirements for the next generation of deep space missions cover a wide range from the kilowatt to the milliwatt.
Engineering topics
Publications and source records attributed to Fleurial, J. P..
Electrical power requirements for the next generation of deep space missions cover a wide range from the kilowatt to the milliwatt.
The integration of new more efficient thermoelectric materials developed at the Jet Propulsion Laboratory into a new high-performance segmented thermoelectric generator has been reported earlier.
Advanced thermoelectric microdevices integrated into thermal management packages and low power, electrical source systems are of interest for a variety of space and terrestrial applications.
A systematic search for advanced thermoelectric materials was initiated at JPL several years ago to evaluate candidate materials which includes consideration of the following property attributes: (1) semiconducting properties; (2) large Seebeck coefficient; (3) high carrier mobility and high electrical conductivity; (4) low lattice thermal conductivity; and (5) chemical stability and low vapor pressure. Through this candidate screening process, JPL identified several families of materials as promising candidates for improved thermoelectric materials including the skutterudite family. As part of an ongoing effort to develop skutterudite materials with lower thermal conductivity values, several solid solutions and filled skutterudite materials were investigated under the effort sponsored by DOE. The efforts have primarily focused on: (1) study of existence and properties of solid solutions between the binary compounds CoSb3 and IrSb3, and RuSb2Te, and (2) CeFe(4-x)Sb12 based filled compositions. For the solid solutions, the lattice thermal conductivity reduction was expected to be reduced by the introduction of the Te and Ru atoms while in the case of CeFe(4-x)Ru(x)Sb12 based filled compositions. For the solid solutions, the lattice thermal conductivity reduction was expected to be reduced by the introduction of the Te and Ru atoms while in the case of CeFe(4-x)Ru(x)Sb12 filled compositions, the reduction would be caused by the rattling of Ce atoms located in the empty voids of the skutterudite structure and the substitution of Fe for Ru. The details of the sample preparation and characterization of their thermoelectric properties are reported in this report.
Thermoelectric energy conversion efficiency is directly related to the temperature difference over which the device operates, its average temperature of operation and the transport properties of the thermocouple material represented by ZT, the dimensionless figure of merit.
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One of the new approaches for developing thermoelectric materials with superior figures of merit is to look at materials which can be referred to as 'rattling' semiconductors.
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A low lattice themal conductivity is one of the conditions required to achieve high thermoelectric figures of merit. Several low themal conductivity materials were identified and developed over the past few years at JPL, including filled skutterudites and Zn (sub 4) Sb (sub 3) - based materials.
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Materials with the skutterudite crystal structure possess attractive transport properties and have a good potential for achieving ZT values substantially larger than for state-of-the-art thermoelectric materials.
A low lattice thermal conductivity is one of the requirements to achieve high thermoelectric figures of merit.
Due to the combined increase in circuit integration and chip power dissipation, there is a rapidly growing demand for solving the thermal management issues of power microelectronics.
B-Zn(sub 4-x)Cd(sub x)Sb(sub 3) was recently identified at the Jet Propulsion Laboratory as a new high performance p-type thermoelectric material with a maximum dimensionless thermoelectric figure of merit ZT of 1.4 at a temperature of 673K.
Recent experimental results on semiconductors with the skutterudite crystal structure show that these materials possess attractive trasport properties and have a good potential for achieving ZT values substantially larger than for state-of-the-art thermoelectic materials.
We have prepared and measured the electrical resistivity, Seebeck coefficient, and thermal conductivity of the Chevrel material Mo(2)Re(4)Se(8) in the 300-1000K temperature range.
Despite their relatively low efficiency, thermoelectric generators are used in a limited number of industrial applications where they are preferred to other energy conversion devices because of their high reliability, low maintenance and long life, in particular when considering harsh environments.