JPS58180076A - Novel polyphase thermoelectric alloy and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to new and improved materials for thermoelectric applications and methods of making the same.

The world's resources of energy-producing fossil fuels have been depleted at an ever-increasing rate. This reality not only creates an energy crisis and shocks the world economy, but also threatens world peace and stability.

The solution to the energy crisis lies in the development of new fuels and more efficient technologies to use them. To this end, the present invention addresses issues such as energy storage, power generation, pollution, and the generation of new business opportunities by developing new materials for use in devices that provide more electricity.

One part of the solution for the development of a permanent and economical energy transition lies in the thermoelectric domain, where electricity is generated by heat. It has been estimated that two-thirds of our energy, from vehicle exhaust or power plants, for example, is wasted and released into the environment. So far,
There are no significant climate impacts from this thermal pollution. but,
As global energy consumption increases, the effects of thermal pollution will ultimately lead to partial melting of polar basins and concomitant sea level rise. Using waste heat for power generation can directly reduce this thermal pollution, independent of the energy source.

The performance of a thermoelectric device can be expressed in terms of the efficiency index (Z) of the material forming the device, where Z is defined as, where Z is in units of x 103 , where S is the coefficient in μv/C and K is mW.
/CrIL-', and σ is (Ω-
cIIL)-' is the electrical conductivity.

From the above, in order for a material to be suitable for thermoelectric power conversion, it must have a large value of thermoelectric Seebeck coefficient), high electrical conductivity (σ), and low thermal conductivity. Furthermore, there are two components for the thermal conductivity ■: the lattice (1ait, 1ce) component Kl, and the electrical component K
e. In nonmetals, ni/ is dominant, and K
It is this component that mainly determines the value of .

Stated another way, for a material to be effective in thermoelectric power conversion, it is important that carriers diffuse easily from hot to cold contacts while maintaining a temperature gradient. Therefore, high electrical conductivity is required in parallel with low thermal conductivity.

Thermoelectric power conversion has not found widespread application in the past. The main reason for this is that prior art thermoelectric materials suitable for commercial applications were crystalline in structure. Those crystalline materials most suitable for thermoelectric devices are difficult to manufacture because of their poor mechanical properties and sensitivity to compositional changes. This occurs because they are based on elements such as tellurium and selenium, which are natural glass formers. The growth, control, and mechanical stability of these crystals has therefore led to being an insurmountable problem to date. In particular, materials with high performance index (Z) are commonly made from chalcogenides, such as tellurium compounds, which are notoriously difficult to grow in high quality single crystals. Even when such crystals grow, they contain large defect densities and are often unstable. Moreover, they are usually not very stoichiometric. For all these reasons, controlled doping has proven extremely difficult.

Large values of conductivity cannot be achieved. Most importantly, due to crystal symmetry, thermal conductivity cannot be adjusted by metamorphism.

Even in the case of conventional polycrystalline approaches, the problem of single crystal materials still predominates. However, new problems also arise due to polycrystalline grain boundaries, which give these +I materials relatively low electrical conductivity. Furthermore, the production of these materials is also difficult to control as a result of their more complex crystalline structure. Chemical modification or toping of these '+tJJx's is a particular problem due to the problems mentioned above.

The best known existing polycrystalline thermoelectric material is (B
1. S b ) 2 T e 3 + P b T
e and 5i-Ge. This (st, 5b)2Te
3 represents a continuous solid solution system in which the relative amounts of B1 and Sb are from 0 to 100%.

The 5i-Ge material is best suited for high temperature applications ranging from 60 ρC to 1000c and exhibits a satisfactory Z above 700c. PbTe polycrystalline material exhibits its best performance index in the 600C to 500C range. None of these materials are suitable for applications in the 1oor to 600C range.

This is indeed unfortunate, since it is at this temperature of 100-600C that a wide range of Class M waste heat applications are found. Among such applications are geothermal waste heat and waste heat from internal combustion or diesel engines, such as in trucks, notebooks, and automobiles. This type of application is costly since all of this heat is waste heat. Heat in the higher temperature range must be generated intentionally with other fuels and not as waste heat from odors.

The thermoelectric material of the present invention is not a single phase crystalline material, but is a disorderly ordered material. These materials are multiphase materials having both an amorphous phase and multiple crystalline phases.

This type of material is a good thermal insulator. They contain grain boundaries of various transition phase phases whose composition varies from that of the matrix crystallites to that of each phase in the grain boundary region. These grain boundaries are highly irregular and contain thermally resistant phases whose transition phase phases provide high resistance to heat conduction. In contrast to conventional materials K,
This material is designed such that grain boundaries define regions containing conductive phases and provide multiple electrical conduction paths through the Merck material to increase electrical conductivity without substantially affecting heat transfer. Designed. In essence, the materials of the present invention have all of the advantages of polycrystalline materials in desirably low thermal conductivity and crystalline bulk properties. but,
Unlike prior art polycrystalline materials, the disordered multiphase materials of the present invention also have desirably high electrical conductivity.

Therefore, according to the present invention, the product of S2σ for the capability index can be independently maximized with a desirably low thermal conductivity for thermopower generation.

Amorphous materials, representing the highest degree of disorder, have been created for thermoelectric applications. Examples of materials and methods for this purpose include Standard R.

U.S. Patent No. 4, published under the name Opsinski.
177.476, 4,177.474. and 4.17
No. 8,415, disclosed and claimed in US Pat. No. 8,415. The materials disclosed in these patents have a structural configuration with a circumferential rather than a long-range alignment, and an electrical configuration with an energy gap and an electrical activation energy. It is formed in a solid amorphous matrix Ma) IJ Lux. A metamorphic substance having an orbit that interacts with the amorphous matrix arrangement k itself to form an electronic state in the energy gap is added to this amorphous base matrix. This interaction substantially reduces the activation energy of the amorphous matrix material in favor of its electronic configuration, thus substantially increasing the electrical conductivity of the material. The electrical conductivity obtained can be adjusted by the amount of modifier material added to the host matrix. The amorphous matrix normally has intrinsic-like conductivity, and the altered material changes it to extrinsic-like conductivity.

As also disclosed therein, the amorphous host matrix can have lone pairs of electrons with which the orbitals of the metamorphic agent interact to form new electronic states in the energy gap. . In another form,
The host matrix can have predominantly tetrahedral bonds, in which case the modifying agent material is added in a predominantly non-displacement manner so that its orbitals interact with the host matrix.

d-band material and f-pan that add multi-track character
*Boron and carbon as well as boron and carbon can be used as transformation agents to form new electronic states in the energy gap.

As a result of the foregoing, these amorphous thermoelectric materials have substantially increased electrical conductivity. However, since they remain amorphous after metamorphosis, they retain low thermal conductivity and 'I? to 4
It is well suited for thermoelectric applications in the high temperature range above 001:'. 7 These vJ materials are modified at the atomic or microscopic level, so that their atomic composition is substantially changed, providing the independently increased electrical conductivity mentioned above. This-
In contrast, the materials of the present invention are not atomically altered. Rather, they are fabricated to introduce irregular arrangements into the material at a macroscopic level. This disordered arrangement allows various phases, including conductive phases, to be introduced in exactly the same way as atomic transformations in pure amorphous phase materials to provide controlled high electrical conductivity, while Irregular arrangements in other phases give low thermal conductivity. These materials are therefore intermediate between amorphous and ordered polycrystalline materials with respect to their thermal conductivity.

The present invention provides a new and improved material and method for making the same for thermoelectric applications in desired temperature ranges with good thermal conductivity, high electrical conductivity, and low thermal conductivity. . This arm and improved material is also capable of compositionally disordered arrays, transformations, etc., which closely resembles in a macroscopic way the atomic and specular processing methods of truly amorphous objects. It has irregular arrangements, morphological irregularities, and other irregular arrangements, allowing for the incorporation of highly conductive phases that give low thermal conductivity while giving high electrical conductivity.

Between the grain boundaries are macroscopic grain boundary open regions, which also contain various phases including electrically conductive phases and connective inclusions.

This grain boundary open region provides il#i electrical conductivity and there are many electrically conductive metamorphic phases present. This grain boundary open region and other phases within the grain boundary provide low thermal conductivity.

This material is made according to the method of the invention by forming a mixture of at least a first and a second multi-element inorganic compound. Generally, at least one of these compounds contains at least one element with a high electrical conductivity of at least 103, exemplified by, for example, 104 (Ω-1)-1. The mixture is heated to an elevated temperature and then cooled to form a large number of matrix crystals separated by irregularly ordered grain boundaries defining open grain boundary regions containing the highly conductive phase.

The first and second compounds are crystalline in structure but have different geometrical forms. For example, prior to their combination, the first compound can include bismuth, antimony, and tellurium with a rhombohedral crystal structure, and the second compound can include bismuth, antimony, and tellurium with a face-centered cubic crystal structure. can include. Alternatively, the first compound can include bismuth, tellurium, and selenium.

This material can also be made more oxidized by, for example, adding tellurium iodide or cadmium chloride to one of the compounds before mixing.
, 4 tones may also be included.

Therefore, the first object of the present invention is to provide a material for thermoelectric applications with low thermal conductivity and high electrical conductivity, which material is characterized by a phase containing a large number of matrix value crystals. , these crystallites are separated by macroscopic grain boundary open regions containing at least one metamorphic phase introduced therein to increase the electrical conductivity of the material.

A second object of the invention is to provide a method for producing materials for thermoelectric applications with low thermal conductivity and high electrical conductivity, the method comprising at least a first and a second multi-element compound. forming a mixture of , at least one of these compounds containing at least one element with high electrical conductivity; heating this mixture to an elevated temperature; and then cooling the mixture to extract electricity from this mixture. A polyphase consisting of a large number of matrix crystallites separated by macroscopically disordered grain boundary open regions with at least an electrically conductive phase having at least one of the above-mentioned conductive elements. phase solid alloy w
Forming J quality; each process is characterized.

Preferred embodiments of the invention will now be described by way of example with reference to the accompanying drawings.

Honmaruma provides a method for producing a thermoelectric material with a highly selective performance index over a desired temperature range S by introducing the presence of random ordering throughout the material. The materials of the present invention have a disordered arrangement that does not exist in a homogeneous crystal structure. This disordered arrangement exists not only in how the elements combine into their different phases at the atomic level, but also in the macroscopic form Mk, where the material is compositionally disordered. other irregular arrangements, such as irregular arrangements, transformational irregular arrangements, morphological irregular arrangements, or surface irregular arrangements, as well as the creation of unique electrical conduction paths throughout the material to improve electrical conductivity. It has transition graded phases on the surface between phases that provide enhancement, while this irregular arrangement provides low thermal conductivity.

This #3 material has multiphase grain boundary open regions, irregularly arranged grain boundaries, and K
Therefore, it has a three-dimensional irregular arrangement with a large number of separated Ma) IJ sock crystals. This grain boundary open region contains a highly electrically conductive modified phase that creates a large number of conductive paths between mimic crystals throughout the bulk of the material, providing control of electrical conductivity in accordance with the control of the paths; The overall electrical conductivity of a crystalline structure cannot be easily changed.

Randomization in thermoelectric materials can be of varying degrees. Not only is it a single-phase crystalline material, but it also does not show any irregular arrangement.
Therefore, it has substantially fixed factors. Pure amorphous materials have no long-range order and can be modified as described above. The materials of the present invention are multiphase in structure and have substantially more free M than prior art crystalline materials.
It has a regular array, and it has various degrees of unique and irregular arrays. This irregular arrangement may be the result of compositional disorder, in which case the structure is created by combining elements in a manner that changes the distribution of elements in the material from that which occurs naturally. It becomes an array. Compositionally disordered arrangement is due, for example, in the materials of the invention to the presence of crystallites, disordered grain boundaries containing transitional graded phases, and grain boundary open regions containing various complexes and phases of the constituent elements. It is verified by various aspects inside the material, such as:

Transformational disorder in the materials of the invention is evident as the microcrystals, grain boundaries and grain boundary open regions are randomly arranged. These crystallites vary in size and orientation, while the grain boundaries vary in width and length.

Morphological disorder exists in the materials of the present invention because the crystallites are of various shapes with arbitrarily irregular surface morphology. The morphology of grain boundaries also changes randomly.

All of the above results result in the material of the present invention being highly disordered and are the reason for the desirable low thermal conductivity, while the highly conductive phase within the intergranular regions provides unique conductive paths to the microcrystals. electrically conductive paths are provided throughout the entire volume of the material, greatly increasing electrical conductivity, while thermal conductivity remains unaffected; Desirably even decreases. This result is not possible in the case of crystalline materials.

As mentioned above, the electrical conductivity of a material is usually proportional to its thermal conductivity. This is especially true for crystalline materials. In the case of such materials, it is extremely difficult to increase electrical conductivity without simultaneously increasing thermal conductivity. However, because thermal conductivity is more dependent on long-range atomic agglomerates than electrical conductivity, disordered materials can achieve high values of electrical conductivity while maintaining low thermal conductivity.

Another important point is that because stoichiometry and purity are not as cost factors in these materials as they are in conventional materials, greater latitude in manufacturing and lifetime stability is possible. These materials, unlike conventional crystalline or polycrystalline materials, are enhanced by disordered alignment or do not suffer from negative effects.1,-0 One advantage of disordered alignment materials is that they It is more flexible than crystalline materials. This disordered material is therefore able to deform more during expansion and contraction, allowing for greater mechanical stability during heating and cooling cycles of the material.

Generally, and according to the broad scope of the present invention, the first and second compounds exhibit different crystal structures or geometries in the hot ductile alloy obtained by performing the steps as hereinafter disclosed. Promotes and supports the irregularly arranged structure of. Further logically, the more dissimilar the crystal structures or geometries of the first and second adducts, the more favorable the arrangement of the final thermoelectric alloy will result. The resulting disordered arrangement is dominated by matrix crystallites bounded by disordered grain boundaries containing transitional graded phases consisting primarily of the first compound; This is illustrated by the grain boundary open regions between the grain boundaries shown. For example, and according to one embodiment of the invention, the first compound has a rhombohedral crystal structure, for example (Bi, 5b)2T
It is in the class of substances represented by continuous isosolutes of e3. As the first compound, compounds with a diamond-shaped crystal structure, such as 5i-Ge', or compounds with a face-centered cubic crystal structure, such as PbS and PbTe, can also be used. All of these substances and the most famous (B
i, 5b) It is believed that the 2Te3 material is suitable for use in single-source #JK when combined with a second compound of a different crystal structure.

To provide a heterogeneous crystal structure to the first compound having a rhombohedral or diamond-shaped crystal structure, the second compound can be, for example, a material with a face-centered cubic crystal structure. This cypress material, according to one embodiment of the invention, includes the compound Ag25Sb25Te6G. P
J! for the first compound of bTe and PbS! To provide a wood crystal structure, the second compound can be a material with an orthogonally tied crystal structure, such as A g z Te.

The first compound also exhibits a satisfactory Seebeck coefficient since it represents the major part of the material bulk and is therefore the cornerstone component that provides an acceptable Seebeck coefficient of the final thermoelectric material. is preferred. Substances such as chalcogenides 9 of Group VB elements, such as bismuth and/or antimono, inter alia (B i t
S b ) 2 T e , t represents one group of compounds in this building, including lead sulfide (PbS), copper telluride (PbT
All known semiconductor materials, such as the compounds 5i-Ge and 5i-Ge, generally exhibit satisfactory Seebeck coefficients.

Other materials suitable for use as the first compound include materials that have thermoelectric properties and contain Group VIB or Group VB, such as Bj, Sb, and copper-tin telluride.

It is anticipated that crystalline materials other than those disclosed herein will be suitable for use as the first and second components in the present invention. For example, crystalline compounds exhibiting thermoelectric properties, especially those with a Seebeck coefficient of 100 μv/C or greater, may be used. Suitably, such a compound may be combined with a second component of at least two elements capable of forming at least one highly electrically conductive phase when combined; A disordered thermoelectric material should be produced that has a higher electrical conductivity than the first compound alone and/or a lower thermal conductivity than the first compound alone.

When the second compound is combined with the first compound in a relatively small amount or proportion, it alters the electrical and thermal properties of the first component, resulting in a higher electrical conductivity and/or higher electrical conductivity than the first compound alone. It should be possible to produce a thermoelectric material with a lower thermal conductivity than the I-compound monolith.

To modify electrical conductivity, the second compound forms highly conductive phase(s) in the grain boundary open regions when combined with the first compound. These multiconducting phases can be complexes of semiconducting elements, at least one of which is in a higher concentration than the other semiconducting element(s), or a high concentration of highly conductive elements and other can be a complex with an element of low conductivity. Suitable modification compounds are believed to include tellurides and antimonides of Group IB and IB transition metals, and more particularly, binary or ternary tellurides of silver, gold, thallium, and indium. and antimonide.

Compounds that fall within these categories are, for example, AgTe, A
g2're, InSb, AgSb.

A uT e * A u 2 T e + A us
b, T l 2 T e t T j T e ,
T7S b+ and Tl5bTe and, according to one preferred embodiment of the invention, A g 25 S b
z s T e s. It is.

When the second compound is combined with the first compound by the method of the present invention, one significant violet among the elements of the second compound enters the bulk of the first compound and forms a violet in the grain boundary region. Leaving behind a complex of the remaining elements of the two compounds. These complexes have high concentrations of at least one of these elements. If the elements of a second compound are semiconductors when they are in equal proportions, then complexes of these elements are highly conductive when one element is more concentrated than the other element(s). It is. When one element is selectively introduced into the grain, a small portion of it remains in the intergranular regions? is believed to form a highly electrically conductive phase with the 7G cords that are not introduced into the bulk.

A method for forming the multiphase disordered alloy of the present invention.
and a second compound are described herein. The individual compounds are first prepared in solid form by a suitable method.

Thereafter, the first and second components are ground or otherwise crushed into particulate form and mixed together in the desired proportions to form a preferably homogeneous particulate solid mixture. The mixture is then heated to form a melt. Preferably, the mixture is heated to an elevated temperature to partially melt the first compound and partially melt the second compound. More specifically, 1 of the melt! After heating, the melt is preferably cooled using a controlled temperature gradient.

Preferred heating temperatures and/or heating/cooling rates will vary depending on the specific first and second components utilized.

The temperature rise and humidity and the heating and cooling rate affect the morphology and size of IJ lux crystals, the grain boundary open area and the irregular arrangement of grain boundaries, which also affect the thermoelectric properties of the thermal IL injection material of the present invention. may have an impact on. The size of the second component that enters the bulk of the first component may also be related to the nature and rate of heating and cooling. Two ingredients may be required.

The multiphase disordered alloy material of the present invention is preferably formed from heavy metals such as lead, bismuth, antimony, tellurium, and silver. Such heavy metals are notorious for their low thermal conductivity. These types of elements have low thermal conductivity because their phonon transport is reduced.11 The alloys of the present invention are also made from at least first and second multi-element compounds that are made separately and then combined. The first and second compounds are preferably in solid form and are ground into solid particulate form and mixed together in the desired proportions to form a particulate solid mixture. The mixture is then heated to an elevated temperature. and then cooled by drawing through a temperature gradient.

The result of this process is an alloy material whose structure, compositional distribution, and thermal and electrical properties are substantially different from those made from the constituent elements alone. It is anticipated that various combinations of first and second compounds can be obtained and optimized by simple experimentation to determine desired properties. In a preferred embodiment, to make a p-type utility pole alloy, the first compound is bismuth, antimony/tellurium, 10% to 20% bismuth, 2υ
% antimony and 60'j6 atomic proportions of tellurium. Preferably, the first compound contains 10%, 304, and 60% of these elements in atomic percentage, respectively (B1toS
b3oTesg) To create an on-fjli thermal alloy, the first compound is bismuth, tellurium, and selenium, with about 40% bismuth, 42% to 54To(
1) Contains an atomic proportion of tellurium and 184 to 6 qb selenium. The second compound includes at least one highly electrically conductive element, such as silver. The second compound may also include antimony and tellurium.

Silver, antimony, and tellurium compounds contain these elements in atomic ratios of 25%, 25%, and 50%, respectively (A
g 25 S b 25 T e s. ) is preferred. The first and second compounds are separately crushed and ground. After that, the number of compounds decreased from 97% to 99.7596. The second compounds are mixed together in desired proportions in the range H from 6% to 0.25% to form a solid particulate mixture. The mixture is then heated to a suitable temperature increase, eg, from about 600C to 650C, and then cooled by a growth process defined herein as a modified vertical Bridgman process. In this method,
The mixture is placed inside a quartz tube and passed through a temperature gradient from its maximum temperature to chamber 1! l\Take over.

The first compound exemplified by B11oSb3°Te6o has a rhombohedral crystal structure and is a continuous isosolute (Bi, Sbλ
One compound from Tea. Ag25Sb2
The second compound, exemplified by 5Te5G, is also crystalline but has a face-centered cubic crystal structure, which is of course different from the rhombohedral crystal structure of the first compound.

The resulting material scale is not drawn to a scale that allows for a more detailed representation of the large number of matrix crystallites separated by irregularly arranged grain boundaries and grain boundary open regions.

As described by AI, alloy 10 includes a large number of matrix crystallites 12. The microcrystals are separated by grain boundaries 14 having a non)itJllll arrangement and grain boundary open regions 16. These transitional phases vary in composition from that of the matrix crystallites to that of the various phases in the grain boundary regions. The grain boundary open region 16 contains various phases, some of which have a high silver content, a highly conductive metamorphic phase 18, and a microcrystalline intercalated phase.
Even Ij20 is formed. This matrix microcrystal 12
typically has a width on the order of 10 microns, and grain boundary open regions 16 have macroscopic dimensions ranging from 0.1 microns to 6 microns.

Example 1 The alloy just mentioned was specifically made in the following manner.

Three-component system (B11°Sb, oTe, )) and (Ag25
Both Sb 25 T13 s o ) were made by sealing appropriate portions of elementally pure (99.999% purity) in separate K, internal diameter/2 inch (1.27 m) vacuum quartz tubes. These materials were held above the melting temperature of the various elements for several hours and thoroughly mixed several times to ensure complete reaction and homogeneity of the entire liquid. The material was cooled and ground into solid crystalline form. Desired violet for the composition, here 99% B 1s
o Sb s o T e , s o , was weighed in volume on an analytical balance to a 10-' Durham degree. This granular material was placed in a quartz tube with an internal diameter of 4 ia* and a length of 10 cm. The quartz tube is sealed and prepared for the alloy growth process. The alloy is grown by a modified vertical Bridgman method by vertically drawing a quartz tube through a temperature gradient varying from an initial 650C to room temperature 20C. This tube is 30
It is pulled out at a speed of 60 Samurai under a constant temperature gradient of C/am. The grown alloy impot is opened and cut, and 25
It was annealed at 0C for about 20 hours.

This alloy was subjected to Energy Dispergive
@ Analysis (EDS). A vector detection time of less than 100 seconds was used. The result of EDS analysis shows that the composition of matrix microcrystal 12 is essentially (B11°Sb3°T
It was shown that the composition corresponds to that of e 6o ). These crystallites are randomly oriented, have random dimensions, and are randomly shaped, all of which contribute to the desired random arrangement. The region of the fractured grain boundary plane consists of Ag-Te and does not contain antimony (Sb) or bismuth (B1).The ratio of silver to tellurium in the zero intergrain boundary region is markedly violet and 2=
1, so the composition recorded here is A
g 2 T e .

Other complexes of silver and tellurium were also recorded. It was found that some regions within the grain boundaries were composed of 100% tellurium.

The above analysis shows that the alloy of the present invention is highly disordered. This analysis also applies when two separate compounds are combined, Ag2,5b25To.

It was confirmed that the antimony compound was dispersed in Merck, leaving silver and tellurium in the grain boundaries 14 and grain boundary regions 16.

The presence of the highly electrically conductive element silver in the grain boundary open chain region provides a means to obtain high electrical conductivity of the resulting alloy. Also, the highly irregular arrangement of the grain boundaries and the modified phase, which is not highly thermally conductive, including a silver-rich tellurium phase in the grain boundary open regions 16, account for the desired low thermal conductivity of this alloy.

B1□. S 1) s o T 8 s o crystalline compounds are currently available materials used in thermoelectric applications. To illustrate the desired properties that can be obtained from the alloys of the invention, reference may be made to the table below, which includes B 1
, o S b 3o T es. room temperature Seebeck coefficient of the compound), electric conductivity (σ), and lattice (laHlc
e) Thermal conductivity (KJ) of 99% B 1 i oSb according to the method of the invention as described more specifically hereinafter.
aoTf3, io and 1% Ag25Sb25T
Comparison is made to the alloy of the present invention formed from e5°.

S (μV/l') 160 120
(Ω-rz)-' 1250 4000
KIl (mW, 4/K) 15 10
From the table above, it can be seen that the electrical conductivity of the new alloy is 6 times that of the prior art crystalline material, and the thermal conductivity of the new alloy is 2/3 that of the prior art material. Although the Seebeck coefficient of the new alloy is 20% lower than that of the prior art material, the resulting performance index is K higher due to the substantially higher electrical conductivity and substantially lower thermal conductivity. It is therefore seen that the present invention provides greater independent control of critical factors not available with conventional crystalline or polycrystalline materials.

Airen I2J B of 9975 from 97% made by the above method
i □oS ba oT et, o and 0.25 from 3rd place
%Ag25S'b25Tes. All the various alloys with proportions of . Figures 2 to 5
The figure is a graph showing the performance index, electrical conductivity, thermal conductivity, and Seek coefficient for the alloys listed below prepared by the above-described method.

Example 2 (8110S'1oTe40)*, 5+(Ag26S
b25TeSo)O0S6(B110Sb30Te6G
)99 + (Ag2sSb2!Te50)14
(B11Sb30Te!G)98. IS+(Ag25S
b25Te! to) L, 55 (B110Sb30Te!
G)9#+(Ag2sSb25Tθ5o)2 The curves for this various alloys are Ag□Sb25Tf3 s.

[Indicated by the amount of compound mixed in.] As can be seen when comparing the electrical conductivity of the alloy shown in Figure 6 with the thermal conductivity shown in Figure 4, the electrical conductivity of this alloy depends on the amount of the second compound (Ag25Sb2sTe5g) incorporated therein. can be controlled.

Although electrical conductivity can be controlled, thermal conductivity remains substantially the same for each alloy.

It can also be seen from Figure 5 that the Seebeck coefficient appears to decrease slightly with increasing incorporation of the second compound. However, when the incorporation of the second compound reaches 1%,
The Seebeck coefficient remains virtually unchanged.

I in Figure 2! The first line, of course, represents the combined effect of the various factors shown in FIGS. 6 to 5. Here, about 0.5
It is seen that the alloy with % of the second compound exhibits the best performance index up to about 140C. Approximately 140C to 200C
At C, alloys containing about 1 qb of the second compound exhibit the best performance index. Therefore, the alloys of the present invention not only exhibit a good performance index in the all-important temperature range of 100C to 200C (furthermore, these alloys can be controlled in the desired temperature range by incorporation of appropriate amounts of secondary compounds). These beneficial results also reflect stability and ease of fabrication.

Figure 6 shows (B111)Sb30Te@G)9G+(Ag25sb
The product of S σ is shown for the alloy 25Te50)1. It is observed that this product is maximum at 100C.

It is at this point that the jK index of the material begins to reach its maximum value again while the thermal conductivity increases slightly.

Confirming that the concept of the present invention is a general concept, we have discovered that the alloy can include either p-type or n-type beepscents. Among these, p-1[)''-, such as lead, can be used as an n-type dopant in the art (known as tellurium iodide (T e I 4 )). Alternatively, other compounds, such as tellurium, can also be used in the practice of the present invention.T9-nocents, preferably tellurium iodide (T e I 4 ), are added to the first compound during alloy preparation. (B10.Sb3°Te, - is incorporated into the alloy to maximize the 82σ product. For example, only 0.1% and 1% tellurium iodide is required. Examples of compounds such as cadmium chloride (CchCl), zinc chloride (ZnCjz), or mercury chloride (HgGl2) can also be used.

Example 6-10 Figure 7 shows (B110Sb30Te6G)911+(Ag
25sb25Te5G) 10 alloy with a concentration of T e 14 of 0 over a temperature range of about 25r to 200c.
．． The competency index is shown for 2%, 0.3%, 0.4%, 0.5% and 1%.

It is observed here that the alloy exhibits some of the best performance from about 5 Or to about 120 C when incorporating about 0.4% Tel. Approximately 0.2% T e I
Its capability index is best from about 12 DC when including 4. For the entire temperature range shown, alloys containing approximately 0.2% T e I 4 exhibit the best overall performance index. Once again, it is seen that the alloys of the present invention can be tailored according to the present invention to provide particular properties over a desired temperature range.

Example 11 Starting n−fJ! used in this example! The material has a composition of B i 40 T f354 S @ g doped with 0.15% CadO chloride (CdGj2.) and 1% (Ag2.Sb2°Tes.). Alloyed together. This alloy was synthesized for 2FI# at K 800C before being grown in a Bridgman furnace at a rate of 10 s/h. This alloying increased the electrical conductivity (σ), and the Seebeck coefficient 0 had a higher value than that of the starting material B14° T el s 4 S e 6 at temperatures above 150°C. The performance index) had the same temperature behavior as the Seebeck coefficient (S). Therefore, the standard n-type thermoelectric material B1□(Te,5e)3 can be modified as a p-type material by implementing the concepts of the present invention.

Example 12-15 Composition of n-=1111 alloy of Example 12-15: (XX
1% TeI4 doped B'40Te411Se12)9
8'' (Ag25Sb25Te!10)1, and X is 0.0.05°0.10 and 0.20.

These alloys include beep or non-topic compounds of bismuth, tellurium and selenium, and antimony, antimony,
and a second compound of tellurium were separately prepared by first synthesizing the respective constituent elements by weighing them in appropriate proportions, sealing them in a 101 Torr quartz tube, and melting them at 800C for 2 hours. Thereafter, the melt was rapidly cooled. Each of the first compounds was then combined with the second compound in the indicated proportions in the form of a particulate mixture and melted at 800C for several hours. After cooling, each of the four compounds had its own internal diameter of 5 x
It was placed in a quartz tube of m. The quartz tube was evacuated to 101 Torr, heated to approximately 650C, and passed through a temperature gradient of 60°C to 10°C.
I pulled it out to room temperature at Mineshun's speed.

FIG. 8 shows a plot of performance index vs. temperature for each of these alloys and the conventional prior art polycrystalline B1°(Te,5e)3 material. As can be seen, the untopped alloys and the alloys with a predominant tellurium iodide content of 105JT have larger performance indices than the conventional grapes above about 80C, while o, io and 020 Alloys with tellurium iodide by weight have a performance index greater than conventional materials above about 140C.

Alloys with 0.20 weight factor tellurium iodide have the best performance indices above about 200C. Therefore, the performance index can be tailored for a desired temperature range by varying the concentration of vinoce/t.

It is also significant that the alloy with tellurium iodide of 250 CK has a performance index that is more than double that of the conventional material.

This is favorable because the product of capacity index and temperature (ZT) is directly related to the efficiency of a material in converting temperature differences into electrical energy. Therefore, at a temperature of 250C, this alloy is 1
It can be nearly 0.00% more effective.

The n-type alloy of Examples 16-18 had the following composition: 01Ji%
T e I 4 Tofuno'(')Bi 4 oT8
4□Se 1g ) m s + (Ag25Sb25Te
iQ)1 and X is 0. [110° and 0120
be equivalent to.

These alloys were prepared by the same method described above for the preparation of the n-type alloys of Examples 12-15.

FIG. 9 shows the performance index vs. temperature for each of these alloys and the conventional prior art polycrystalline material B1□(Te,5e)a. As can be seen, the untopped alloy has a greater performance index than the conventional material above about 160C. Alloys containing 0.10 and 0.20% tellurium iodide have higher performance indices above about 140C and 175C, respectively.

Undoped alloys have the best performance index above about 220C. FIG. 9 therefore further illustrates that the performance index can be tailored for a particular temperature range by varying the degree of temperature.

Note also that at 250C, the undoped alloy has a performance index nearly twice that of conventional polycrystalline materials. As explained above with respect to Section 8e7, this makes this alloy much more desirable than conventional materials at temperatures relevant to many waste heat applications.

From the foregoing, it can be appreciated that the present invention provides a new and improved alloy and method for making the same for thermoelectric applications. Because these alloys are randomly arranged, their electrical conductivity can be tailored as desired without affecting their thermal conductivity. Additionally, some of the alloys of the present invention are suitable for thermoelectric applications in temperature ranges as low as 100C to 200C. In their wA range, they exhibit a more favorable performance index than previously known crystalline materials, ranging from at least 25q6 to 40 ToK. Ease of manufacture and stability of operation are far superior to conventional materials requiring purity, stoichiometry, and defect control.

Additionally, it is not necessary that the first and second compounds be electrically conductive. In fact, Ag□Sb□T e
s. The compound itself does not exhibit good electrical conductivity. However, when combined with a second compound, the macroscopic transformation of the present invention results in a new and improved thermoelectric alloy with higher electrical conductivity than any of its constituent compounds. Although it is preferred that at least one of these compounds exhibits a suitable Seebeck coefficient, it is also not necessary that one of these compounds is itself a good thermoelectric material. Improved thermoelectricity according to the IJT standard by the method of the present invention? J quality can be fabricated from materials with satisfactory Seebeck coefficients but unsatisfactory electrical and thermal conductivity properties. Furthermore, it is also not necessary that the first and second compounds be rhombohedral and face-centered cubic in their crystal systems. Other geometries are contemplated in the practice of the present invention.

[Brief explanation of drawings]

FIG. 1 is a fragmentary cross-sectional view depicting the structure of a material made according to the method of the invention; FIG. 2 is a graph depicting the capability index vs. temperature for various alloys of the invention; Figure 27 is a graph depicting the electrical conductivity C) versus temperature for various alloys of the present invention; Figure 4 is a graph depicting the thermal conductivity C) versus temperature for various alloys of the present invention; Seebeck coefficient for various alloys of the invention)
FIG. 6 is a graph of Sσ versus temperature for various alloys of the present invention; FIG. 7 is a graph of Sσ versus temperature for various alloys of the present invention containing tellurium iodide at various degrees , ability index c1. ) is a graph depicting the center of temperature vs. temperature: Figure 8 depicts the capability index ■ vs. temperature for the n-type alloys of Examples 12-15 of the present invention containing tellurium iodide of each IE # degree. It is a graph; FIG. 9 is a book depicting the performance index versus temperature for the n-type alloys of Examples 16-19 of the present invention each containing 11 degrees of tellurium iodide. %l'F Applicant Energy Conversion Devices Incorporated FIG I FIG, 2 FIG 3 FIG, 4 11 et al. Name of New Multi-Phase Thermoelectric Alloy and Process for Producing the Same Relationship with the Case of Person Who Amends Patent Applicant Address 4, Agent 5 Sleeve + I', [Claims] Column 6 of Subject Specification 11C , Sode 11-no Uchi'tani (Attachment) (1) The scope of the claims is amended as follows. Materials for thermoelectric applications with high thermal conductivity and high electrical conductivity. This means that the one modified phase controls the electrical conduction independently of the thermal conductivity, so that the matrix of the material (1
2) The material according to claim 1, characterized in that it is modified by: 3. A material according to claim 2, characterized by another phase for independently controlling the thermal conductivity of the material. 4. Material according to claim 6, further characterized in that said further phase is adapted to reduce the thermal conductivity of said material. 6. The above-mentioned microcrystal (12) is at least bismuth, tellurium,
The material according to claim 1, characterized in that it contains antimony and antimony. 6. Material according to claim 1, characterized in that said at least one additional phase contains at least one element with high electrical conductivity. 7゜The material according to any one of claims 1 to 6, characterized in that the above-mentioned material contains at least bismuth, tellurium, antimony and silver.8) IJ lux crystal ( 12) A material according to claim 1, characterized by a grain boundary (14) between the grain boundary open region (16) and said grain boundary comprising transitional graded phases. 96 The transition stage phases described above are similar in composition to the microcrystalline (
9. A material according to claim 8, characterized in that the composition of the phase in the grain boundary open region (16) varies from the composition of 12). 10° forming a mixture of at least a first and a second multi-element compound, at least one of which includes at least one element with high electrical conductivity; heating this mixture to an elevated temperature and humidity; and then cools the mixture and separates the mixture from the mixture by macroscopic irregularly ordered grain boundary open regions having at least an electrically conductive phase having at least one of the above-mentioned elements having high electrical conductivity. (a large number of Ma)
A method for producing a material for thermoelectric applications with low thermal conductivity and high electrical conductivity, characterized by a step of forming a multiphase solid alloy material consisting of a phase of IJ lux crystals. 11. The method of claim 10, wherein the first multi-element compound comprises bismuth, antimony, and tellurium. 12. The method of claim 10 or claim 11, wherein the second multi-element compound comprises silver, antimony, and tellurium. 13. The method of claim 12, wherein said first compound consists of 10 to 20% bismarene, 20 to 60% antimony, and 60% tellurium. 14. The method of claim 16, wherein said second compound consists of 25% silver, 25% antimony, and 50% tellurium. 15. The material of claim 1, wherein said material comprises at least bismuth, tellurium, and selenium. 6. Claim 10, wherein the first multi-element compound contains bismuth, tellurium, and selenium.
The method described in section. 17. The method of claim 16, wherein said second multi-element compound comprises silver, antimony and tellurium. "that's all

Claims (1)

[Claims] 1. A macroscopic grain boundary open region (12) containing a large number of matrix crystals (12) and containing at least one modified phase into which the microcrystals are introduced to increase the electrical conductivity of the material. 16) is separated by tP! f[, a material for thermoelectric applications with low thermal conductivity and high electrical conductivity. 2. One of the above modified phases controls electrical conduction independently of the upper thermal conductivity.
2) The material according to claim 1, characterized in that it is modified by: 3. The material according to claim 2, characterized by one phase for independently controlling the thermal conductivity of the material. 4. Further analogous to adapting another phase of the above to reduce the thermal conductivity of the material, especially, f
f. The material according to claim 3. 5. The microcrystal (12) is at least bismuth, tellurium,
The material according to claim 1, characterized in that it contains antimony and antimony. 6. Material according to claim 1, characterized in that said at least one additional phase contains at least one element with electrical conductivity. 7. The material according to any one of claims 1 to 6, characterized in that said material contains at least bismuth, tellurium, antimony and silver. 8. The method according to claim 1, characterized by a grain boundary between said matrix fine J& (12) and said grain boundary open region (16), and said grain boundary comprises transition graded phases. material. 9. According to claim 8, said transitional phases vary in their composition from the composition of said microcrystals (12) to the composition of said grain boundary open regions (16). material. 10 forming a mixture of at least a first and a second multi-element compound, at least one of which contains at least one element with high electrical conductivity; heating the mixture to an elevated temperature and humidity; and then the mixture is cooled and separated by macroscopic irregularly ordered grain boundary open regions having at least an electrically conductive phase containing at least one of the above-mentioned elements with high electrical conductivity. 11. A method for producing a material for thermoelectric applications with low thermal and electrical conductivity, characterized by steps: forming a multiphase solid alloy material consisting of a large number of matrix crystallite phases. 12. The method of claim 10, wherein the first multi-element compound comprises bismuth, antimony and tellurium. 12. The second multi-element compound comprises silver, antimony,
Claim 1 characterized in that it contains tellurium and tellurium.
The method according to any one of Items 0 and 11. 13. The method of claim 12, wherein the first compound consists of 10 to 20% bismuth, 20 to 60% antimony, and 60% tellurium. 14.% characterized in that said second compound consists of 25% silver, 25% antimony, and 50% tellurium.
! 11! F. The method according to claim 16. 15. The material of claim 1, wherein said material contains at least bismuth, tellurium, and selenium. 16. The method of claim 10, wherein the first multi-element compound comprises bismuth, tellurium, and selenium. 17. The method of claim 16, wherein the second multi-element compound comprises silver, antimony, and tellurium.