CN1807666A

CN1807666A - Nanometer SiC/ Bi2Te3 base thermoelectric material preparation method

Info

Publication number: CN1807666A
Application number: CN 200510130794
Authority: CN
Inventors: 张波萍; 李敬锋; 赵立东; 刘静
Original assignee: Tsinghua University; University of Science and Technology Beijing USTB
Current assignee: Tsinghua University; University of Science and Technology Beijing USTB
Priority date: 2005-12-30
Filing date: 2005-12-30
Publication date: 2006-07-26
Anticipated expiration: 2025-12-30
Also published as: CN100351409C

Abstract

The invention discloses a pyroelectric material preparing method of nanometer SiC/Bi2Te3 radical in the energy resource and material technique domain, which comprises the following steps: using high-purity Bi powder and nanometer SiC as raw material; compounding Bi2Te3 chemical compound superfine powder by mechanical alloy; using discharge plasma sintering process to sinter Bi2Te3 predecessor fines of doping nanometer SiC granule for block. The job step is composed of deploying raw material, mechanical alloying, discharge plasma sintering, example detecting. The art work is easy; time of compounding chemical compound is short and temperature of sintering is low.

Description

A kind of nano SiC/Bi 2Te 3The preparation method of base thermoelectricity material

Technical field:

The invention belongs to the energy and material technical field, a kind of nano SiC/Bi particularly is provided ₂Te ₃The preparation method of base thermoelectricity material, relate to mechanical alloying (Mechanical Alloying, MA) and discharge plasma sintering (Sparkplasma sintering, SPS) preparation technology.

Background technology:

1823, Thoums Seebeck found thermoelectric effect first, thereby had begun human research and application to thermoelectric material.Bi ₂Te ₃Base thermoelectricity material is the best thermoelectric material of performance under the room temperature, also be to study the earliest one of the most sophisticated thermoelectric material, have bigger Seebeck coefficient and lower thermal conductivity, ZT is about 1 under the room temperature, great majority freeze and all are to adopt this class material by temperature difference converting electrical energy element at room temperature at present, so Bi ₂Te ₃The focus that remains present research of base thermoelectricity material.The researcher is to Bi both at home and abroad ₂Te ₃Base thermoelectricity material has carried out number of research projects.

From the technology of preparing aspect, along with a lot of methods of progressive generation of science and technology, as hydrothermal synthesis method, mechanical alloying, the hot method of flux, SPS method, zone melting method etc.; Mechanical alloying method is because technology is simple, advantage such as save time receives very big concern, (S.S.Kim such as S.S.Kim, S.Yamamoto, T.Aizawa, thermoelectric properties ofanisotropy-controlled p-type Bi-Te-Sb system via bulk mechanical alloying and shear extrusion, Journal of Alloys and Compounds, 375 (2004) 107-113) utilize mechanical alloying after hot pressed method produce the Bi-Te-Sb block thermoelectric material, improved the thermoelectricity capability of material, but pressure sintering can not make sample have very high density, thereby can influence conductivity of electrolyte materials; At present, about adopting the SPS method to prepare Bi ₂Te ₃The bibliographical information of sill seldom, the current research of thermoelectric material study group of Beijing University of Technology shows, adopts SPS agglomerating CoSb ₃Under the prerequisite of high-compactness (99.8%), obtained the following alloy block of average grain size 100nm, seen that thus the SPS technology is at Bi ₂Te ₃Application prospect on the sill.

Add the alloying element aspect, prepared ternary, quaternary even multicomponent alloy.Rare earth element is owing to have that special out-shell electron is arranged and China has rich in natural resources and caused very big concern.Zhao new recruits etc. have prepared La ₁₅Bi ₃₄Te ₅₁Alloy, the special energy band structure of analysis revealed rare earth element causes bigger Seebeck coefficient, and research is gone up this group and has been applied for patent (CN03151275.5) in this respect, but the ZT value of the thermoelectric material of rare earth doped back gained is only about 0.2.

The material nano aspect becomes the focus of nearest research, (L.Ni, X.B.Zhao, et al, synthesis andthermoelectric properties of Bi such as X.B.Zhao ₂Te ₃Based nanocomposites, Journal of Alloys and Compounds, 397 (2005) 317-321) utilize hydrothermal synthesis method to prepare the Bi of 10～30nm ₂Te ₃Powder, and to Bi ₂Te ₃Base thermoelectricity material mixes, and adopts pressure sintering to prepare block materials, works as Bi ₂Te ₃When nanometer powder content was 10wt.%, obtaining maximum ZT value was 0.83, but the density of sample is not high, if mechanical property and Seebeck coefficient that density improves thermoelectric material all can obtain very big improvement.This group is at nano level Bi ₂Te ₃Preparation and Bi thereof ₂Te ₃The research aspect of base nano pyroelectric material has obtained very big progress, and has applied for multinomial patent, (CN03151276.3, CN200310109130.0, CN200410073387.X).

From present research, on the preparation method, adopt MA and SPS method to prepare Bi ₂Te ₃Base thermoelectricity material is not also reported.Technical at doped nanoparticle, to Bi ₂Te ₃Base thermoelectricity material carries out nano SiC granule and mixes also less than report.The present invention is directed to Bi in decades ₂Te ₃The ZT value of base thermoelectricity material is paced up and down about 1 and very low mechanical property always, adopts MA and SPS method to prepare nano SiC/Bi ₂Te ₃Base thermoelectricity material mainly is to modify Bi by mixing ₂Te ₃The energy band structure of sill and the control of technology made Bi ₂Te ₃Thereby the thermal conductivity that reduces grain refine improves thermoelectricity capability and improves mechanical property.

Summary of the invention:

Purpose of the present invention is to provide a kind of nano SiC/Bi ₂Te ₃The preparation method of base thermoelectricity material reaches thermoelectricity capability and the mechanical property that improves material by the doping of nano SiC granule by design and control to preparation technology.

The present invention is a raw material with high-purity Bi powder, Te powder and nano SiC, by the synthetic Bi of mechanical alloying (MA) ₂Te ₃The compound fines utilizes discharge plasma sintering (SPS) technology with dopen Nano SiC particulate Bi again ₂Te ₃The fine powder sintering of forerunner becomes block.Concrete processing step comprises:

1, configuration material: adopt high-purity Bi, Te simple substance as initial feed, press Bi: Te=2: 3 atomic ratios batching, mix nano SiC granule according to different volume percent simultaneously, volume percent is 0.0～1.0%.

2, mechanical alloying: raw material is put into ball grinder, and feed protection of inert gas, prevent raw material powder oxidation in the MA process, dry grind under protection of inert gas, rotating speed is 100～500rpm, and the time is 15min～96h.The dry grinding back adds dehydrated alcohol as the medium wet-milling, and rotating speed is 50～300rpm, and the time is that 15min～12h prevents powder agglomates, makes its ball milling more even.The powder oven dry of alloying is obtained dry powder.Bake out temperature is 20～200 ℃, and the time is 4～20h.After Fig. 1 represents alloying, contain different volumes per-cent SiC particulate Bi ₂Te ₃X-ray diffractogram of powder illustrates and has finished Bi ₂Te ₃Synthetic.

3, discharge plasma sintering: the SiC/Bi after will synthesizing ₂Te ₃The material powder graphite jig of packing into is put sintering in the discharge plasma sintering stove into, and the sintering environment is a vacuum, and vacuum tightness is 4～7Pa.Carry out sintering under certain temperature, pressure, soaking time, sintering temperature is 200～500 ℃, and soaking time is 2～8min, and sintering pressure is 20～60MPa, and heat-up rate is 40 ℃～180 ℃/min.Fig. 2 is the displacement and the time relation curve of pressure head in the SPS sintering process, and as can be seen from Figure 2 400 ℃ of insulation 5min can obviously improve sample axial shrinkage amount under the 50MPa pressure, improve sample density, thereby improve the hardness of material.Fig. 3 is at 400 ℃, the sample SEM fracture comparison diagram of different SiC content under the 50MPa condition, and Fig. 3 shows that the increase grain fineness number along with SiC content reduces, the hardness of material is along with increase.Fig. 4 is at 400 ℃, the sample ZT value curve of different SiC content under the 50MPa condition, and wherein working as SiC content is 0.5%, during 400K, maximum ZT value reaches 1.07.

4, sample detection: after taking out sample, after with sand paper sample surfaces being polished, carry out the thing identification of phases and microstructure analysis, and carry out the thermoelectricity capability test.

The invention has the advantages that:

(1) synthetic compound time weak point can obtain fine forerunner's powder; (2) sintering temperature is low, and sintering time is short, can obtain tiny, uniform tissue, and can keep the state of nature of starting materials; (3) can obtain high compactedness material; (4) can obtain high mechanical property and thermoelectricity capability.

Description of drawings

After Fig. 1 is alloying of the present invention, different SiC granule content Bi ₂Te ₃The X-ray diffractogram of powder.

Fig. 2 is the displacement and the time relation curve of pressure head in the SPS sintering process under the different process of the present invention.

Fig. 3 is 400 ℃ of the present invention, and 50MPa condition SiC content is 0.0% sample SEM fracture comparison diagram.

Fig. 4 is 400 ℃ of the present invention, and 50MPa condition SiC content is 0.1% sample SEM fracture comparison diagram.

Fig. 5 is 400 ℃ of the present invention, and 50MPa condition SiC content is 0.5% sample SEM fracture comparison diagram.

Fig. 6 is 400 ℃ of the present invention, and 50MPa condition SiC content is 1.0% sample SEM fracture comparison diagram.

Fig. 7 is at 400 ℃, the sample ZT value curve of different SiC content under the 50MPa condition.

Embodiment:

At first adopt mechanical alloying method (MA) preparation Bi ₂Te ₃Presoma fines, dopen Nano SiC particle simultaneously.This method is that simple substance with high-purity Bi element and Te element is according to the atomic ratio proportioning; the nano SiC granule of while and different content is put into planetary high-energy ball mill together and carry out mechanical alloying under the Ar gas shiled; the dry grinding synthetic compound carries out wet-milling again, and oven dry at last obtains Bi ₂Te ₃The base thermoelectricity material fines utilizes discharge plasma sintering process (SPS) with dopen Nano SiC particulate Bi again ₂Te ₃The fine powder sintering of forerunner becomes block, and the sintering process of taking adopts different sintering pressures under the certain temperature condition.Under certain sintering pressure, adopt different sintering temperatures to carry out sintering.Sintering temperature is 300～500 ℃, and soaking time is 2～8min, and sintering pressure is 20～60MPa.

Table 1 has provided several preferred embodiments of the present invention:

Preferred embodiment	SiC content (V%)	Ball milling speed (rpm)	The ball milling time (h)	Sintering temperature (℃)	Sintering pressure (MPa)	Relative density (%)	Microhardness (GPa)	Power factor (10 ^-4Wm ^-1K ^-2)	Maximum ZT
Preferred embodiment	SiC content (V%)	Ball milling speed (rpm)	The ball milling time (h)	Sintering temperature (℃)	Sintering pressure (MPa)	Relative density (%)	Microhardness (GPa)	Power factor (10 ^-4Wm ^-1K ^-2)	Maximum ZT	Embodiment
1	0.0	100	0.4	200	20	95.4	59.2	14.6	0.56	Embodiment
1	0.0	100	0.4	200	20	95.4	59.2	14.6	0.56	Embodiment 2	0.5	100	3	200	20	94.3	61.5	13.5	0.58
Embodiment 3	1.0	100	24	200	20	91.5	634	12.3	0.66	Embodiment 2	0.5	100	3	200	20	94.3	61.5	13.5	0.58
Embodiment 3	1.0	100	24	200	20	91.5	634	12.3	0.66	Embodiment 4	5.0	100	48	200	20	82.9	67.3	12.1	0.45
Embodiment 5	10.0	100	96	200	20	81.6	69.5	11.3	0.38	Embodiment 4	5.0	100	48	200	20	82.9	67.3	12.1	0.45
Embodiment 5	10.0	100	96	200	20	81.6	69.5	11.3	0.38	Embodiment 6	0.0	350	0.4	350	50	97.6	62.4	19.1	0.72
Embodiment 7	0.5	350	3	350	50	97.1	67.4	15.9	0.81	Embodiment 6	0.0	350	0.4	350	50	97.6	62.4	19.1	0.72
Embodiment 7	0.5	350	3	350	50	97.1	67.4	15.9	0.81	Embodiment 8	1.0	350	24	350	50	95.6	72.3	18.6	0.80
Embodiment 9	5.0	350	48	350	50	94.8	78.9	13.3	0.65	Embodiment 8	1.0	350	24	350	50	95.6	72.3	18.6	0.80
Embodiment 9	5.0	350	48	350	50	94.8	78.9	13.3	0.65	Embodiment 10	10.0	350	96	350	50	89.6	80.5	12.4	0.59
Embodiment 11	0.0	450	0.4	400	50	98.2	62.8	21.2	1.02	Embodiment 10	10.0	350	96	350	50	89.6	80.5	12.4	0.59
Embodiment 11	0.0	450	0.4	400	50	98.2	62.8	21.2	1.02	Embodiment 12	0.5	450	3	400	50	97.4	68.0	18.7	1.07
Embodiment 13	1.0	450	24	400	50	96.9	74.8	19.5	0.76	Embodiment 12	0.5	450	3	400	50	97.4	68.0	18.7	1.07
Embodiment 13	1.0	450	24	400	50	96.9	74.8	19.5	0.76	Embodiment 14	5.0	450	48	400	50	95.0	83.3	15.3	0.72
Embodiment 15	10.0	450	96	400	50	93.6	80.7	14.1	0.56	Embodiment 14	5.0	450	48	400	50	95.0	83.3	15.3	0.72
Embodiment 15	10.0	450	96	400	50	93.6	80.7	14.1	0.56	Embodiment 16	0.0	500	0.4	500	60	95.6	60.6	19.3	0.90
Embodiment 17	0.5	500	3	500	60	94.4	72.8	19.0	0.94	Embodiment 16	0.0	500	0.4	500	60	95.6	60.6	19.3	0.90
Embodiment 17	0.5	500	3	500	60	94.4	72.8	19.0	0.94	Embodiment 18	1.0	500	24	500	60	92.4	75.3	17.1	0.77
Embodiment 19	5.0	500	48	500	60	92.2	78.4	15.5	0.52	Embodiment 18	1.0	500	24	500	60	92.4	75.3	17.1	0.77
Embodiment 19	5.0	500	48	500	60	92.2	78.4	15.5	0.52	Embodiment 20	10.0	500	96	500	60	91.9	79.6	13.9	0.50

In sum, method of the present invention is promptly produced forerunner's powder by mechanical alloying, carries out the SPS sintering again, prepared nano SiC granule doping Bi ₂Te ₃Base thermoelectricity material has good thermoelectricity capability and mechanical property.

Claims

1, a kind of nano SiC/Bi ₂Te ₃The preparation method of base thermoelectricity material is characterized in that: with high-purity Bi powder, Te powder and nano SiC is raw material, is combined to Bi by mechanical alloy ₂Te ₃The compound fines utilizes discharge plasma sintering process with dopen Nano SiC particulate Bi again ₂Te ₃The fine powder sintering of forerunner becomes block.

2, according to the described preparation method of claim 1, it is characterized in that: processing step comprises:

A, configuration raw material: adopts high-purity Bi, Te simple substance as initial feed, press Bi: Te=2: 3 atomic ratios are prepared burden, and the while is 0.0～10.0% to mix nano SiC granule according to volume percent;

B, mechanical alloying: raw material is put into ball grinder, and feed protection of inert gas, dry grinding, rotating speed is 100～500rpm, and the time is 15min～96h.The dry grinding back adds dehydrated alcohol as the medium wet-milling, and rotating speed is 50～300rpm, and the time is 15min～12h; The powder oven dry of alloying is obtained dry powder, and bake out temperature is 20～200 ℃, and the time is 4～20h;

C, discharge plasma sintering: the SiC/Bi after will synthesizing ₂Te ₃The material powder graphite jig of packing into is put sintering in the discharge plasma sintering stove into, and the sintering environment is a vacuum, and vacuum tightness is 4～7Pa; Sintering temperature is 200～500 ℃, and soaking time is 2～8min, and sintering pressure is 20～60MPa, and heat-up rate is 40 ℃～180 ℃/min;

D, sample detection: after taking out sample, after with sand paper sample surfaces being polished, carry out the thing identification of phases and microstructure analysis, and carry out the thermoelectricity capability test.