JP6493170B2 - Thermoelectric material - Google Patents
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- JP6493170B2 JP6493170B2 JP2015225471A JP2015225471A JP6493170B2 JP 6493170 B2 JP6493170 B2 JP 6493170B2 JP 2015225471 A JP2015225471 A JP 2015225471A JP 2015225471 A JP2015225471 A JP 2015225471A JP 6493170 B2 JP6493170 B2 JP 6493170B2
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- 239000000463 material Substances 0.000 title claims description 38
- 239000002019 doping agent Substances 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 description 15
- 239000002994 raw material Substances 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 238000001878 scanning electron micrograph Methods 0.000 description 11
- 239000000203 mixture Substances 0.000 description 10
- 229910052787 antimony Inorganic materials 0.000 description 9
- 229910052797 bismuth Inorganic materials 0.000 description 9
- 229910052751 metal Inorganic materials 0.000 description 9
- 239000002184 metal Substances 0.000 description 9
- 238000000034 method Methods 0.000 description 9
- 239000000843 powder Substances 0.000 description 9
- 239000011777 magnesium Substances 0.000 description 8
- 229910021338 magnesium silicide Inorganic materials 0.000 description 8
- YTHCQFKNFVSQBC-UHFFFAOYSA-N magnesium silicide Chemical compound [Mg]=[Si]=[Mg] YTHCQFKNFVSQBC-UHFFFAOYSA-N 0.000 description 8
- 238000005245 sintering Methods 0.000 description 8
- 239000000126 substance Substances 0.000 description 7
- 229910019018 Mg 2 Si Inorganic materials 0.000 description 6
- 239000008188 pellet Substances 0.000 description 6
- 239000012071 phase Substances 0.000 description 6
- 239000010453 quartz Substances 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 6
- 229910019064 Mg-Si Inorganic materials 0.000 description 5
- 229910019406 Mg—Si Inorganic materials 0.000 description 5
- 238000002844 melting Methods 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 150000002739 metals Chemical class 0.000 description 4
- 238000002156 mixing Methods 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 125000004429 atom Chemical group 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000007791 liquid phase Substances 0.000 description 3
- 239000002210 silicon-based material Substances 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 229910052732 germanium Inorganic materials 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 230000001771 impaired effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 238000007088 Archimedes method Methods 0.000 description 1
- 229910002909 Bi-Te Inorganic materials 0.000 description 1
- 229910017082 Fe-Si Inorganic materials 0.000 description 1
- 229910017133 Fe—Si Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 239000004570 mortar (masonry) Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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- Silicon Compounds (AREA)
Description
本発明は熱電材料に関する。詳しくは、特定のドーパントを含有するマグネシウムシリサイド系の熱電材料に関する。 The present invention relates to a thermoelectric material. Specifically, the present invention relates to a magnesium silicide-based thermoelectric material containing a specific dopant.
工場、自動車、及び電子機器等から排出される熱を有効利用するため、熱エネルギーを電気エネルギーに変換する熱電素子が検討されている。 In order to effectively use heat discharged from factories, automobiles, electronic devices, and the like, thermoelectric elements that convert thermal energy into electrical energy have been studied.
熱電素子に用いられる材料としては、例えば、Ｍｇ−Ｓｉ（マグネシウムシリサイド）系、Ｂｉ−Ｔｅ系、Ｐｂ−Ｔｅ系、ＳＩ−Ｇｅ系、及びＦｅ−Ｓｉ系等が知られている。 As materials used for thermoelectric elements, for example, Mg—Si (magnesium silicide), Bi—Te, Pb—Te, SI—Ge, and Fe—Si are known.
例えば、特許文献１には、Ｍｇ−Ｓｉ系の熱電材料にドーパントを含有させることにより、熱電変換特性をより高める技術が開示されている。 For example, Patent Document 1 discloses a technique for further improving thermoelectric conversion characteristics by adding a dopant to an Mg—Si-based thermoelectric material.
Ｍｇ−Ｓｉ系材料に含有されるドーパントとしては、例えば、Ｂ、Ｐ、Ｓｂ、Ｂｉ、Ｃｕ、Ａｕ、Ｆｅ、Ａｌ等が知られている。しかしながらこれらの金属の多くは、融点が高いため、低温（例えば１，０００℃未満）の熱処理条件下で主相であるマグネシウムシリサイドと固溶化することは困難である。 For example, B, P, Sb, Bi, Cu, Au, Fe, Al and the like are known as dopants contained in the Mg—Si based material. However, since many of these metals have high melting points, it is difficult to form a solid solution with magnesium silicide, which is the main phase, under heat treatment conditions at a low temperature (for example, less than 1,000 ° C.).
ドーパントとして一般に使用される金属の融点を下記に示す。
Ｂ：２，３００℃
Ａｌ：６６０．３２℃
Ｐ：５９０℃
Ｓｂ：６３０．７℃
Ｂｉ：２７１℃
Ｃｕ：１，０８３℃
Ａｕ：１，０６４℃
Ｆｅ：１，５３５℃
The melting points of metals generally used as dopants are shown below.
B: 2,300 ° C
Al: 660.32 ° C.
P: 590 ° C
Sb: 630.7 ° C
Bi: 271 ° C
Cu: 1,083 ° C.
Au: 1,064 ° C
Fe: 1,535 ° C
従って、従来技術においては、ドーパントを含有する熱電材料は１，０００℃以上の高温における熱処理を経て製造されている。しかし、このような高温は、主相を構成するＭｇの融点（１，０９０℃）に近く、或いはこれを超えるから、Ｍｇの蒸発による組成ズレ、不純物の混入、酸化等の不都合を伴い、熱電性能が損なわれる場合が多い。 Therefore, in the prior art, a thermoelectric material containing a dopant is manufactured through a heat treatment at a high temperature of 1,000 ° C. or higher. However, such a high temperature is close to or exceeding the melting point (1,090 ° C.) of Mg constituting the main phase, and therefore, there are inconveniences such as compositional deviation due to evaporation of Mg, mixing of impurities, oxidation, etc. Performance is often impaired.
ドーパントとして一般に使用される金属の融点を下記に示す。
Ｂ：２，３００℃
Ａｌ：６６０．３２℃
Ｐ：５９０℃
Ｓｂ：６３０．７℃
Ｂｉ：２７１℃
Ｃｕ：１，０８３℃
Ａｕ：１，０６４℃
Ｆｅ：１，５３５℃
The melting points of metals generally used as dopants are shown below.
B: 2,300 ° C
Al: 660.32 ° C.
P: 590 ° C
Sb: 630.7 ° C
Bi: 271 ° C
Cu: 1,083 ° C.
Au: 1,064 ° C
Fe: 1,535 ° C
融点が低いＡｌ、Ｓｂ、Ｂｉ等は、低温熱処理におけるドーパントとして有望である。しかし、いずれも熱拡散速度が遅いため、マグネシウムシリサイド相中に安定に固溶せず、主相と分離した相として存在する。図１５に、ＳｂをドープしたＭｇ−Ｓｉ系材料の断面ＳＥＭ像を示す。この図の白く見える部分はＳｂ濃度が高い領域である。 Al, Sb, Bi and the like having a low melting point are promising as dopants in low-temperature heat treatment. However, in any case, since the thermal diffusion rate is slow, the magnesium silicide phase does not stably dissolve, but exists as a phase separated from the main phase. FIG. 15 shows a cross-sectional SEM image of the Mg—Si based material doped with Sb. The portion that appears white in this figure is a region with a high Sb concentration.
本発明は、上記のような現状に鑑みてなされた。その目的は、低温における熱処理によって容易に固溶化することのできるマグネシウムシリサイド系の熱電材料を提供することである。 The present invention has been made in view of the above situation. The object is to provide a magnesium silicide-based thermoelectric material that can be easily dissolved by a heat treatment at a low temperature.
本発明者らは、上記の目的を達成すべく鋭意検討を行った。その結果、特定の金属元素を特定の割合で組み合わせて用いることにより、低温処理によって容易に固溶化してｎ型半導体性を発現するマグネシウムシリサイド系熱電材料が得られることを見出し、本発明を完成させた。 The present inventors have intensively studied to achieve the above object. As a result, it has been found that a magnesium silicide thermoelectric material that can be easily solid-solved by low-temperature treatment and exhibit n-type semiconductor properties can be obtained by using a specific metal element in combination at a specific ratio, and the present invention has been completed. I let you.
本発明は、Ｍｇ２Ｓｉ中に０．２〜１．０ａｔ％のドーパントを含有し、
前記ドーパントがＳｂｘＢｉ１−ｘ（ｘ＝０．１〜０．６）である
ことを特徴とする、熱電材料に関する。
The present invention contain 0.2～1.0At% of dopant into Mg 2 Si,
The dopant is Sb x Bi 1-x (x = 0.1 to 0.6), and relates to a thermoelectric material.
本発明によると、低温処理によって容易に固溶化してｎ型半導体性を発現するマグネシウムシリサイド系熱電材料が提供される。 According to the present invention, there is provided a magnesium silicide thermoelectric material that is easily solid-solved by low-temperature treatment and exhibits n-type semiconductor properties.
以下、本発明に係る熱電材料及びその製造方法の実施形態を詳細に説明する。なお、以下に示す実施形態は、本発明を限定するものではない。 Hereinafter, embodiments of a thermoelectric material and a manufacturing method thereof according to the present invention will be described in detail. In addition, embodiment shown below does not limit this invention.
本発明の熱電材料は、Ｍｇ２Ｓｉ中に０．２〜１．０ａｔ％のドーパントを含有する。このドーパントはＳｂｘＢｉ１−ｘ（Ｘ＝０．１〜０．６）である。 The thermoelectric material of the present invention contains 0.2 to 1.0 at% dopant in Mg 2 Si. This dopant is Sb x Bi 1-x (X = 0.1 to 0.6).
Ｍｇ２Ｓｉは、これらの元素の一部がＧｅ、Ｓｎ等の他の元素で置換されていてもよい。 In Mg 2 Si, a part of these elements may be substituted with other elements such as Ge and Sn.
上記の化学式中のｘは、熱電変換のパワーファクターＰＦ及び無次元性能指数ＺＴの双方を、従来技術に比べて有意に高く発現させるために、０．１〜０．６の範囲から選択されることが好ましい。また、Ｍｇ２Ｓｉ中のドーパントの含有量は、マグネシウムシリサイドの熱電特性を減殺しない範囲でドーパントの添加効果を効果的に発現させるとの観点から、０．２〜１．０ａｔ％の範囲から選択されることが好ましい。ここで、ドーパントの添加量とは、熱電材料中に含有される全金属原子（Ｓｉを含む）中に占める、Ｓｂ及びＢｉの合計の原子数の割合である。 X in the above chemical formula is selected from the range of 0.1 to 0.6 in order to express both the power factor PF of thermoelectric conversion and the dimensionless figure of merit ZT significantly higher than those of the prior art. It is preferable. Further, the content of the dopant in Mg 2 Si is selected from the range of 0.2 to 1.0 at% from the viewpoint of effectively exhibiting the effect of adding the dopant within a range that does not reduce the thermoelectric properties of magnesium silicide. It is preferred that Here, the addition amount of the dopant is a ratio of the total number of atoms of Sb and Bi in all metal atoms (including Si) contained in the thermoelectric material.
本発明の熱電材料におけるドーパントとしては、Ｓｂ及びＢｉ以外に、Ｂ、Ｐ、Ｃｕ、Ａｌ、Ａｕ、Ｆｅ等の他のドーパント元素を含んでいてもよい。 As a dopant in the thermoelectric material of this invention, other dopant elements, such as B, P, Cu, Al, Au, Fe, may be included other than Sb and Bi.
熱電材料中の酸素原子の含有量（残存酸素濃度）は、０．４６ｗｔ％以下とすることが好ましい。残留酸素濃度がこの範囲にあれば、材料中の移送の発生が抑制され、且つ熱電性能を高く維持することができるため、好ましい。 The oxygen atom content (residual oxygen concentration) in the thermoelectric material is preferably 0.46 wt% or less. If the residual oxygen concentration is within this range, the occurrence of transfer in the material is suppressed, and the thermoelectric performance can be maintained high, which is preferable.
上記のような組成の熱電材料は、比較的低温における熱処理で容易に固溶化して生成することができ、しかもＰＦ及びＺＴの熱電性能に優れる。従って本発明の熱電材料は、熱電素子の性能向上及びコストの低減の双方に資するものである。 The thermoelectric material having the composition as described above can be easily solidified by heat treatment at a relatively low temperature and is excellent in thermoelectric performance of PF and ZT. Therefore, the thermoelectric material of the present invention contributes to both improvement in performance of the thermoelectric element and reduction in cost.
以下、本発明の熱電材料の製造方法について説明する。以下に記載する方法は、本発明の熱電材料を製造するための方法の一例であり、本発明の熱電材料を以下に記載の方法によって製造されたものに限定する趣旨ではない。 Hereinafter, the manufacturing method of the thermoelectric material of this invention is demonstrated. The method described below is an example of a method for producing the thermoelectric material of the present invention, and is not intended to limit the thermoelectric material of the present invention to those produced by the method described below.
本発明の熱電材料は、原料金属を混合して原料混合物を調製し、好ましくはこれをペレット状に成形した後、熱処理することにより、製造することができる。熱処理後に更に焼結処理を行うことも、好ましい態様である。 The thermoelectric material of the present invention can be produced by preparing a raw material mixture by mixing raw metal, and preferably heat-treating it after forming it into a pellet. It is also a preferred embodiment that a sintering process is further performed after the heat treatment.
原料混合物中の原料金属の混合割合は、熱電材料における所望の組成に準じて適宜に設定されてよい。 The mixing ratio of the raw material metal in the raw material mixture may be appropriately set according to the desired composition of the thermoelectric material.
例えば、Ｍｇ：Ｓｉの比は、原子比として２：１とすることができる。ここで、Ｍｇの使用割合を理論当量から少し過剰になるように設定することも好ましい態様である。この場合の過剰量は任意であるが、例えば１０ａｔ％以下、好ましくは７ａｔ％の数値を例示することができる。 For example, the Mg: Si ratio can be 2: 1 as an atomic ratio. Here, it is also a preferable aspect that the usage ratio of Mg is set to be slightly excessive from the theoretical equivalent. The excess amount in this case is arbitrary, but a numerical value of, for example, 10 at% or less, preferably 7 at% can be exemplified.
Ｓｂ及びＢｉは化学式ＳｂｘＢｉ１−ｘにおける所望のｘの値を考慮した混合割合で、Ｓｂ及びＢｉの合計量が熱電材料中に含有される全金属原子（Ｓｉを含む）に対して０．２〜１．０ａｔ％となる範囲で選択される。 Sb and Bi are mixing ratios considering a desired value of x in the chemical formula Sb x Bi 1-x , and the total amount of Sb and Bi is 0 with respect to all metal atoms (including Si) contained in the thermoelectric material. It is selected in the range of 2 to 1.0 at%.
これら以外の任意添加成分の原料も、原料混合物に混合されてよい。 Raw materials of optional additional components other than these may also be mixed in the raw material mixture.
原料混合物は、熱処理に際して任意の形状（例えばペレット状）に成形することが好ましい。熱処理は、絶対圧として好ましくは１０ｋＰａ以下の真空下で行うことが、不要な酸素の取り込みを抑制できる点で適切である。熱処理温度は１，０００℃以下とすることができ、好ましくは８９０℃以下とすることができる。熱処理時間は任意であるが、例えば２０時間の数値を例示することができる。 The raw material mixture is preferably formed into an arbitrary shape (for example, a pellet shape) during the heat treatment. It is appropriate that the heat treatment is performed under a vacuum of preferably 10 kPa or less as an absolute pressure in that unnecessary oxygen uptake can be suppressed. The heat treatment temperature can be 1,000 ° C. or less, and preferably 890 ° C. or less. Although the heat processing time is arbitrary, the numerical value of 20 hours can be illustrated, for example.
熱処理後の材料は、次いで、焼結処理を行うことが好ましい。このとき、所謂「つなぎ」として、例えばＡｌを例えば２ｗｔ％添加することも好ましい態様である。 The material after the heat treatment is then preferably subjected to a sintering treatment. At this time, as a so-called “tethering”, it is also a preferable aspect to add, for example, 2 wt% of Al, for example.
焼結処理は、例えば放電プラズマ焼結等の適宜の焼結方法によることができる。 The sintering treatment can be performed by an appropriate sintering method such as discharge plasma sintering.
このようにして本発明の熱電材料を製造することができる。本発明の熱電材料は、例えば、熱電変換モジュール、熱電冷却、光通信等の分野における熱電素子として好適に使用することができる。 In this way, the thermoelectric material of the present invention can be produced. The thermoelectric material of the present invention can be suitably used as a thermoelectric element in fields such as thermoelectric conversion modules, thermoelectric cooling, and optical communication.
以下、実施例によって本発明を更に具体的に説明する。しかしながら本発明は、以下の実施例に限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.
以下の実施例及び比較例における原料金属としては、以下の市販品を使用した。
Ｍｇ：（株）高純度化学研究所製、品名「ＭＧＥ０２ＰＢ純度２Ｎ５」、１８０μｍ以下粉末
Ｓｉ：（株）高純度化学研究所製、品名「ＳＩＥ１９ＰＢ純度３Ｎｕｐ」、４５μｍ以下粉末
Ｓｂ（比較例２以外）：（株）高純度化学研究所製、品名「ＳＢＥ１３ＰＢ純度２Ｎ」、３８μｍ以下粉末
Ｓｂ（比較例２）：液相還元法により合成した粒径＜０．１μｍのＳｂ粉末
Ｂｉ：（株）高純度化学研究所製、品名「ＢＩＥ１１ＰＢ純度３Ｎ」、１〜２μｍ粉末
Ａｌ：（株）高純度化学研究所製、品名「ＡＬＥ１１ＰＢ純度３ＮＧ」、３μｍ粉末
The following commercial products were used as raw material metals in the following examples and comparative examples.
Mg: manufactured by Kojundo Chemical Laboratory Co., Ltd., product name “MGE02PB purity 2N5”, 180 μm or less powder Si: manufactured by Kojundo Chemical Laboratories Co., Ltd., product name “SIE19PB purity 3 Nup”, 45 μm or less powder Sb (other than Comparative Example 2) ): Manufactured by Kojundo Chemical Laboratory Co., Ltd., product name “SBE13PB purity 2N”, powder of 38 μm or less Sb (Comparative Example 2): Sb powder with particle size <0.1 μm synthesized by liquid phase reduction method Bi: Co., Ltd. High purity chemical laboratory product name “BIE11PB purity 3N”, 1-2 μm powder Al: High purity chemical laboratory product name “ALE11PB purity 3NG”, 3 μm powder
＜実施例１＞
（１）熱電材料の製造
Ｍｇ４．０００ｇ及びＳｉ２．０７６ｇ（Ｍｇ：Ｓｉ＝２：１（原子比）からＭｇが７ａｔ％過剰となる割合）、並びにＳｂ０．０５８ｇ及びＢｉ０．０５０ｇ（ドーパント量０．３ｗｔ％、ＳｂｘＢｉ１−ｘにおけるｘ＝０．６）を秤量し、混合して原料混合物を得た。この原料混合物を１００ＭＰａの圧力でプレスして、直径１０ｍｍのペレット１６とした（図２）。
<Example 1>
(1) Manufacture of thermoelectric material Mg 4.00g and Si 2.076g (Mg: Si = 2: 1 (atomic ratio) to Mg at a ratio of 7at% excess), Sb 0.058g and Bi 0.050g (dopant amount 0. 3 wt%, x = 0.6 in Sb x Bi 1-x ) was weighed and mixed to obtain a raw material mixture. This raw material mixture was pressed at a pressure of 100 MPa to form pellets 16 having a diameter of 10 mm (FIG. 2).
このペレット１６をカーボン坩堝１４内に収納し、コック１２を備えた石英管１０内に設置した（図１）。次いで、石英管１０の内部を絶対圧１０ｋＰａに減圧し、真空封止した。真空封止した石英管１０をＳＵＳ製耐熱容器１８内に収納したうえで（株）シリコニット製の炉内に設置し、炉内温度８９０℃において２０時間の熱処理を行った。このときの温度履歴を図４に示した。 The pellet 16 was stored in a carbon crucible 14 and installed in a quartz tube 10 provided with a cock 12 (FIG. 1). Next, the inside of the quartz tube 10 was decompressed to an absolute pressure of 10 kPa and vacuum sealed. The vacuum-sealed quartz tube 10 was housed in a SUS heat-resistant container 18 and then placed in a siliconit furnace, and heat-treated at a furnace temperature of 890 ° C. for 20 hours. The temperature history at this time is shown in FIG.
上記の熱処理後の石英管１０をグローブボックス内で割り、熱処理後の材料を回収した。 The quartz tube 10 after the heat treatment was divided in a glove box, and the material after the heat treatment was recovered.
上記で回収した材料に、２ｗｔ％のＡｌを混合し、乳鉢で１０分間粉砕混合を行い、熱電材料の粉末を得た。この粉末の１ｇを採り、１５ｍｍφのパンチ・ダイスを用いて８００℃、２０分間の放電プラズマ焼結を行うことにより、熱電材料の試料を得た。この焼結時の温度履歴を図５に示した。 The material collected above was mixed with 2 wt% of Al, and pulverized and mixed for 10 minutes in a mortar to obtain a thermoelectric material powder. A sample of thermoelectric material was obtained by taking 1 g of this powder and performing discharge plasma sintering at 800 ° C. for 20 minutes using a 15 mmφ punch and die. The temperature history during this sintering is shown in FIG.
得られた試料の断面ＳＥＭ像を図８に示した。 A cross-sectional SEM image of the obtained sample is shown in FIG.
（２）熱電材料の評価
上記で得た試料を研磨及び切断して、アドバンス理工（株）製の熱電特性評価装置「ＺＥＭ−３」を用いて、５００℃における熱電特性におけるパワーファクターＰＦ及び無次元性能指数ＺＴを測定した。また、ＮＥＴＺＳＣＨ社製「ＭｉｃｒｏＦｌａｓｈ」及びＴＡ Ｉｎｓｔｒｕｍｅｎｔｓ社製「ＤＳＣ Ｑ１００」を用いて、熱伝導率を測定した。試料の密度はアルキメデス法により測定した。評価結果は、表１に示した。
(2) Evaluation of thermoelectric material The sample obtained above was ground and cut, and the power factor PF in the thermoelectric characteristics at 500 ° C. and nothing were measured using the thermoelectric characteristic evaluation device “ZEM-3” manufactured by Advance Riko Co., Ltd. The dimensional figure of merit ZT was measured. Further, thermal conductivity was measured using “MicroFlash” manufactured by NETZSCH and “DSC Q100” manufactured by TA Instruments. The density of the sample was measured by the Archimedes method. The evaluation results are shown in Table 1.
＜実施例２〜４及び比較例１〜３＞
Ｓｂ及びＢｉの仕込み量を変更して、ＳｂｘＢｉ１−ｘにおけるｘの値を表１に記載のとおりに変更した他は、実施例１と同様にして、実施例２〜４及び比較例１〜３試料を調製し、評価した。ここで、ドーパント量は０．３ａｔ％を維持した。得られた試料の断面ＳＥＭ像を図９〜１４に、評価結果を表１に、それぞれ示した。表１には、試料中の残存酸素濃度も合わせて示した。
<Examples 2 to 4 and Comparative Examples 1 to 3>
Examples 2 to 4 and Comparative Example were the same as Example 1 except that the amounts of Sb and Bi were changed and the value of x in Sb x Bi 1-x was changed as shown in Table 1. 1-3 samples were prepared and evaluated. Here, the dopant amount was maintained at 0.3 at%. Cross-sectional SEM images of the obtained samples are shown in FIGS. 9 to 14 and the evaluation results are shown in Table 1, respectively. Table 1 also shows the residual oxygen concentration in the sample.
なお、比較例２におけるＳｂ原料としては、液相還元法により合成した粒径＜０．１μｍのＳｂ粉末を用いた。 In addition, as the Sb raw material in Comparative Example 2, Sb powder having a particle size of <0.1 μm synthesized by a liquid phase reduction method was used.
また、ＳｂｘＢｉ１−ｘにおけるｘに対してパワーファクターＰＦをプロットしたグラフを図６に示した。更にｘに対して無次元性能指数ＺＴをプロットしたグラフを図７に示した。 Moreover, the graph which plotted the power factor PF with respect to x in Sb x Bi 1-x is shown in FIG. Further, a graph plotting the dimensionless figure of merit ZT against x is shown in FIG.
比較例で得られた熱電材料は、パワーファクターＰＦ及び無次元性能指数ＺＴの双方において、実施例の熱電材料に比べて劣っていた。これは、Ｓｂ及びＢｉが、Ｍｇ２ＳｉのＳｉサイトに固溶せずに単独層として存在していることに起因するものと考えられる。比較例２では、Ｓｂのナノ粒子を用いることによるＳｂの固溶化促進を狙ったが、奏功しなかった。これは、Ｓｂナノ粒子の合成を液相法によったため、Ｓｂの純度が９５％程度と低く、この不純物がＭｇ２Ｓｉ相中に存存して熱電性能を損なったものと推察される。 The thermoelectric material obtained in the comparative example was inferior to the thermoelectric material of the example in both the power factor PF and the dimensionless figure of merit ZT. This is considered to be due to the fact that Sb and Bi are not dissolved in the Si site of Mg 2 Si but exist as a single layer. In Comparative Example 2, although Sb solid solution promotion by using Sb nanoparticles was aimed, it was not successful. This is presumably because the synthesis of Sb nanoparticles was based on the liquid phase method, and the purity of Sb was as low as about 95%, and this impurity was present in the Mg 2 Si phase and the thermoelectric performance was impaired.
これに対して実施例で得られた熱電材料は、パワーファクターＰＦ及び無次元性能指数ＺＴの双方が優れた結果を示した。本開示の方法によって合成された熱電材料は、Ｓｂ及びＢｉの固溶化が促進されたためと推察される。 In contrast, the thermoelectric materials obtained in the examples showed excellent results in both power factor PF and dimensionless figure of merit ZT. It is inferred that the thermoelectric material synthesized by the method of the present disclosure has promoted the solid solution of Sb and Bi.
１０ 石英管
１２ コック
１４ カーボン坩堝
１６ 原料混合物のペレット
１８ ＳＵＳ製耐熱容器
DESCRIPTION OF SYMBOLS 10 Quartz tube 12 Cock 14 Carbon crucible 16 Raw material mixture pellet 18 SUS heat-resistant container
Claims (1)
前記ドーパントがＳｂｘＢｉ１−ｘ（ｘ＝０．３〜０．６）である
ことを特徴とする、熱電材料。 Containing 0.2～1.0At% of dopant in mg 2 Si,
A thermoelectric material, wherein the dopant is Sb x Bi 1-x (x = 0.3 to 0.6).
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