Synthesis of New Thermoelectric Materials Using Modulated Elementary Reactants

1998 ◽  
Vol 545 ◽  
Author(s):  
Heike Sellinschegg ◽  
Joshua R. Williams ◽  
Steven P. Maxwell ◽  
Douglas Sillars ◽  
David C. Johnson
Keyword(s):  
Crystal Structure ◽  
Electrical Conductivity ◽  
Low Temperature ◽  
Reaction Intermediates ◽  
Ternary Compounds ◽  
Low Temperature Annealing ◽  
Modulated Elemental Reactants ◽  
Ternary Metal ◽  
Elemental Reactants ◽  
Binary Compounds

AbstractModulated elemental reactants have been used to synthesize metastable ternary compounds with the skutterudite crystal structure. The initial reactants are made up of multiple repeats of a unit containing elemental layers of a ternary metal, iron or cobalt (or a combination of these two) and antimony. The elemental layers interdiffuse upon low temperature annealing and form amorphous reaction intermediates. In this paper we target the compounds PbxFe4−yCoySb12. On annealing at temperatures between 12° and 150° C (depending on the composition) crystallization of the skutterudite structure occurs. The compounds are only kinetically stable, decomposing into a mixture of binary compounds upon annealing past a temperature of about 600°C. Preliminary data for the Seebeck coefficient and the electrical conductivity was collected The thermoelectric properties of the lead cobalt antimony skutterudite - films were measured as a function of lead occupancy.

Synthesis of New Thermoelectrics Using Modulated Elemental Reactants

1997 ◽  
Vol 478 ◽  
Author(s):  
Marc D. Hornbostel ◽  
Heike Sellinschegg ◽  
David C. Johnson
Keyword(s):  
Crystal Structure ◽  
X Ray Diffraction ◽  
Systematic Screening ◽  
X Ray ◽  
Low Temperature Annealing ◽  
Modulated Elemental Reactants ◽  
Ternary Metal ◽  
Elemental Reactants ◽  
Binary Compounds ◽  
New Compounds

AbstractA series of new, metastable ternary crystalline compounds with the skutterudite crystal structure have been synthesized using modulated elemental reactants. The initial reactants are made up of multiple repeats of a ˜25Å thick unit containing elemental layers of the desired ternary metal, iron and antimony. Low temperature annealing (150°C) results in interdiffusion of the elemental layers to form amorphous reaction intermediates. Annealing these intermediates at temperatures between 200°C and 250°C results in exothermic crystallization of the desired skutterudite crystal structure. Most of the new compounds prepared are only kinetically stable, decomposing exothermically to form thermodynamically more stable mixtures of binary compounds and elements. Low angle x-ray diffraction studies show that the resulting films are exceedingly smooth. These films have an ideal geometry for measuring properties of importance for thermoelectric devices—the Seebeck coefficient and the electrical conductivity. Thermal conductivity can be measured using a modification of the 3ω technique of Cahill. Samples can be produced rapidly, allowing for systematic screening and subsequent optimization as a function of composition and doping levels.

The Synthesis of Metastable Skutterudites and Crystalline Superlattices

2000 ◽  
Vol 626 ◽  
Author(s):  
Heike Sellinschegg ◽  
Joshua R. Williams ◽  
Gene Yoon ◽  
David C. Johnson ◽  
Mike Kaeser ◽  
...  
Keyword(s):  
Low Temperature ◽  
Binary Compound ◽  
Decomposition Temperature ◽  
Lattice Parameters ◽  
Low Temperature Annealing ◽  
Cobalt Compounds ◽  
Ternary Metal ◽  
Diffraction Patterns ◽  
Binary Compounds ◽  
Synthetic Approaches

ABSTRACTWe have used controlled crystallization of elementally modulated reactants to prepare a series of kinetically stable, crystalline skutterudites (M'xM4Sb12 where M' = vacancy, RE, Hf,…; M = Ni, Fe, Co) and crystalline superlattices composed of promising thermoelectric materials. For the bulk synthesis of skutterudites, low angle diffraction data demonstrates that the elemental layers interdiffuse at temperatures below 150°C. Nucleation of the skutterudite structure occurs with at large exotherm on annealing at temperatures below 200°C regardless of the ternary metal. All of the metastable ternary compounds and the new metastable binary compounds were found to decompose exothermically on higher temperature annealing. The decomposition temperature ranged from 250°C for the binary compound NiSb3 to above 550°C for the rare earth containing cobalt compounds. The occupation of the ternary site was found to depend on the composition of the initial reactant and was varied from 0 to 1. Full occupancy typically required an excess of the filling cation. The lattice parameters of the compounds prepared at low temperatures are distinctly smaller than those prepared using traditional synthetic approaches. High temperature annealing converts the lattice parameters of the low temperature compounds to those prepared at higher temperatures using traditional synthetic approaches. Diffraction patterns of crystalline superlattices containing skutterudites prepared using elementally modulated reactants show splitting of high angle diffraction maxima as well as the presence of the expected low angle diffraction pattern from a supperlattice. The skutterudite superlattices are stable with respect to low temperature annealing.

Rational Synthesis of The Metastable Compounds BixCo4-xFexSb12

1998 ◽  
Vol 547 ◽  
Author(s):  
Joshua R. Williams ◽  
Joanna Hass ◽  
Heike Sellinschegg ◽  
David C. Johnson
Keyword(s):  
Title Compound ◽  
Phonon Scattering ◽  
Reaction Products ◽  
Ternary Compounds ◽  
Modulated Elemental Reactants ◽  
Exothermic Decomposition ◽  
Metastable Compounds ◽  
Elemental Reactants ◽  
Binary Compounds ◽  
Modulated Elemental Reactant

AbstractThe synthesis of many targeted ternary compounds using conventional synthesis approaches has been unsuccessful because the ternary compounds are thermodynamically unstable with respect to disproportionation to a mixture of binary compounds. Typically these compounds have been synthetic targets based on predictions of enhanced properties. The ternary skutterudites with formula M'xM4Sbl2 (where M' = La, Lu, Y) are prime examples. Compounds with this structure have been found to be very promising thermoelectric materials having both good electrical properties and low thermal conductivities. Inserting heavy M' atoms into this crystal structure has been predicted to further decrease the thermal conductivity by increased phonon scattering. Attempts to make the title compound using conventional synthesis approaches failed due the formation of binary compounds as reaction products. Using modulated elemental reactants we were able to prepare the title compound at 160°C. Annealing at temperatures above 500°C resulted in exothermic decomposition into binary compounds. The Bi containing compounds are therefore thermodynamically unstable with respect to disproportionation at all temperatures. The amount of Bi can be varied by varying the composition of the starting modulated elemental reactant. Preliminary measurements to determine the variation of electrical conductivity and Seebeck coefficient as a function of bismuth content are presented.

The Use of Superlattice Reactants in The Synthesis of Ternary CU‐NB‐SE Compounds

1994 ◽  
Vol 346 ◽  
Author(s):  
Marc D. Hornbostel ◽  
Masafumi Fukuto ◽  
David C. Johnson
Keyword(s):  
Low Temperature ◽  
Thermodynamic Stability ◽  
Binary Systems ◽  
Cluster Compounds ◽  
Reaction Intermediates ◽  
Ternary Compounds ◽  
Controlled Crystallization ◽  
Binary Compounds

ABSTRACTThe low temperature interdiffusion of superlattice reactants of the binary systems niobium‐selenium and copper‐selenium and the ternary copper‐niobium‐selenium were explored to synthesize amorphous reaction intermediates. Controlled crystallization of this intermediate, which depends upon nucleation energetics rather than the thermodynamic stability of the final product, was used as we attempted to prepare ternary niobium cluster compounds. We present data demonstrating the ability to prepare amorphous ternary intermediates without the formation of crystalline binary compounds as reaction intermediates. Crystallization of the amorphous intermediate resulted in the formation of known ternary compounds directly, also without the formation of binary compounds.

Effects of mechanical grinding and low temperature annealing on crystal structure of Er5Si4

2013 ◽  
Vol 556 ◽  
pp. 127-134 ◽  
Author(s):  
Q. Cao ◽  
L.S. Chumbley ◽  
Y. Mudryk ◽  
M. Zou ◽  
V.K. Pecharsky ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Low Temperature ◽  
Mechanical Grinding ◽  
Low Temperature Annealing

ChemInform Abstract: Low Temperature Synthesis Using Modulated Elemental Reactants: A New Metastable Ternary Compound, NixMoSe2.

ChemInform ◽  
2010 ◽  
Vol 33 (36) ◽  
pp. no-no
Author(s):  
Polly A. Berseth ◽  
Thomas A. Hughes ◽  
Robert Schneidmiller ◽  
Arwyn Smalley ◽  
David C. Johnson
Keyword(s):  
Low Temperature ◽  
Ternary Compound ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Modulated Elemental Reactants ◽  
Elemental Reactants

Low temperature synthesis using modulated elemental reactants: a new metastable ternary compound, NixMoSe2

2002 ◽  
Vol 4 (5) ◽  
pp. 717-722 ◽  
Author(s):  
Polly A. Berseth ◽  
Thomas A. Hughes ◽  
Robert Schneidmiller ◽  
Arwyn Smalley ◽  
David C. Johnson
Keyword(s):  
Low Temperature ◽  
Ternary Compound ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Modulated Elemental Reactants ◽  
Elemental Reactants

Bulk Synthesis of Completely and Partially Sn filled CoSb3 Using the Multilayer Repeat Method

2000 ◽  
Vol 626 ◽  
Author(s):  
Heike Sellinschegg ◽  
David C. Johnson ◽  
Michael Kaeser ◽  
Terry M. Tritt ◽  
George S. Nolas ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Physical Properties ◽  
Repeat Unit ◽  
Phonon Modes ◽  
Filled Skutterudite ◽  
Modulated Elemental Reactants ◽  
Wide Range ◽  
Elemental Reactants ◽  
Binary Compounds ◽  
Thermal Conductivities

ABSTRACTFilled skutterudite compounds possess very low thermal conductivities due to the scattering of a wide range of phonon modes caused by a loosely bound cation incorporated in a cavity of the structure. The inclusion of such a filler cation causes several synthetic difficulties since the desired compounds are thermodynamically unstable with respect to disproportionation. Modulated elemental reactants were used in this study to circumvent these difficulties. SnxCo4Sb12 samples with x=0.5 and nearly 1.0 were synthesized using this method. To prevent nucleation of unwanted binary compounds, the repeat unit made up of elemental layers was less than 20 angstroms 500mg of each sample were produced, allowing for the samples to be hot pressed into a pellet. Structural analysis as well as measurements of the physical properties are presented.

Low-Temperature Synthesis of TiC, Mo2C, and W2C from Modulated Elemental Reactants

2001 ◽  
Vol 13 (11) ◽  
pp. 3876-3881 ◽  
Author(s):  
Christopher Johnson ◽  
Heike Sellinschegg ◽  
David C. Johnson
Keyword(s):  
Low Temperature ◽  
Low Temperature Synthesis ◽  
Temperature Synthesis ◽  
Modulated Elemental Reactants ◽  
Elemental Reactants
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