CN102856485A - Three-layer composite structural material for refrigerating semiconductors - Google Patents

Abstract

The invention provides 'a three-layer composite structural material for refrigerating semiconductors', and belongs to the technical field of refrigeration of semiconductors. The three-layer composite structural material comprises three thin layers of refrigerating materials, physical parameters of the refrigerating materials, such as a seebeck coefficient, conductivity and heat conductivity, are properly separated spatially, parameter configurations of the three thin layers of refrigerating materials are optimized according to self functions, a main parameter of each thin layer of refrigerating material is highlighted, and the three thin layers of refrigerating materials are combined to form an integral optimized structure. The optimized composite structure replaces an existing single uniform structure, the technical bottleneck caused by interaction of parameters in the uniform structure is broken through, the scheme is a novel energy-saving and environment-friendly composite material manufacturing scheme, and a novel method is provided for manufacturing semiconductor refrigerating materials and components.

Description

A kind of three-layer composite structure material for semiconductor refrigerating

Title of the present invention is " a kind of three-layer composite structure material for semiconductor refrigerating ", and a kind of new method for preparing refrigerating material and refrigeration device is provided, and belongs to the technical field of semiconductor refrigerating.Semiconductor refrigerating is named again thermoelectric cooling, thermoelectric cooling, is a kind of solid-state refrigeration modes of green.Its advantage is that volume is little, lightweight, pollution-free, noiseless, the life-span is long, reliability is high, environment protecting and power-saving, many application are especially arranged, such as the cooling of electronic device, photoelectric device, automobile cold, hot two-purpose case, water dispenser, red wine cabinet etc. in the refrigerating field of small-power, the little temperature difference.But the shortcoming of semiconductor refrigerating is also apparent in view, and namely to compare Energy Efficiency Ratio not high with traditional refrigeration modes, and cost is also somewhat expensive.In order to overcome these shortcomings, the scholars of countries in the world have done various explorations and research in half a century in the past.The direction of these researchs is mainly manifested in following two aspects:

The first, research and develop new block thermoelectric material.The tellurium bismuth alloy is the best thermoelectric material of the near room temperature of generally acknowledging, present most thermoelectric cooling devices all use this class material.The dimensionless merit figue of this class material is generally all less than 1, and is best only 0.9, ^[1]-[2], also rest on so far the level in the eighties of last century sixties.Much scholars think, this class material few of potentiality can dig, so sight is invested CoSb ₃, Zn ₄Sb ₃, metal silicide and NaCo ₂O ₄On new material, and obtained some effects, ^[3]-[5], but also have very long distance from practical application.

Second, with the current material low-dimensional, do not change the chemical composition of existing thermoelectric material, just original three-dimensional block form is become the low-dimensional forms such as quantum well, superlattice, quantum wire, quantum dot, rely on the property advantage of charge carrier under bound state (such as, near the state density rising Fermi level), interface phonon scattering enhancing and modulation doping improve the many factors such as mobility, the merit figue of raising thermoelectric material.Adopt low dimensional structures to count from the Hicks and Dresselhouse proposal that takes the lead in, only 20 years so far, this respect was just obtained the progress that attracts people's attention ^[5]But, these work still are in the experimental study stage so far, do not have the commodity device to come out, and illustrate in technology and cost to also have very large obstacle to overcome.So, all things considered, the development situation of semiconductor refrigerating also is not very optimistic.

According to our research, the bottleneck master that the block refrigerating material is used is if it were not for the performance issue of material itself, but the unreasonable structure of material and device, it be the reasons are as follows: all block thermoelectric materials all are homogeneous textures so far, quality is characterized by merit figue Z and dimensionless merit figue ZT.

Wherein α is the Seebeck coefficient of material, and σ is the conductivity of material, and κ is the thermal conductivity of material.The below illustrates take n type material as example how bottleneck causes.Semiconductor Physics ^[6]Show, the size of these three parameters is respectively:

Seebeck coefficient

Wherein, κ _bBe Boltzmann constant, q is electron charge, and γ is that dispersion factor is (for the character scattering ), Nc is the electronic state density (intrinsic properties by material determines) at the bottom of the conduction band, n is conduction band electron concentration.As seen, the order of magnitude of α is the subtraction function of electron concentration n, and n is larger, and the absolute value of α is less.

Conductivityσ=nq μ _n(2)

μ wherein _nBe electron mobility, determined by factors such as material category, temperature and impurity defects.As seen, σ is directly proportional with electron concentration n, and n is larger, and σ is also larger.

Thermal conductivity κ=κ _L+ κ _e(3)

κ wherein _LBe lattice thermal conductivity, by the factors such as intrinsic properties, temperature and the defective decision of material, account for the major part of thermal conductivity.κ _eBe Electron Heat conductance, κ _e=L σ T (4)

Wherein L is Lorentz lorentz's constant, and T is temperature.

Obviously, thermal conductivity κ is conductivityσ's increasing function, and σ is larger, and κ is also larger.

Can find out from above four formula, concerning the block materials of even structure, mass parameter α, σ and κ are mutual restriction, and be conflicting, and σ is larger, and α will be less, and κ is also larger.So the merit figue of the refrigerating material of even structure is difficult to improve.This is the basic reason that causes present thermoelectric material quality technology bottleneck.After this uniform blocks structural material cut into element, top electrode was done at two ends again, has just become common semiconductor refrigerating assembly, and the elementary cell of assembly is galvanic couple, and the merit figue of block materials is not high, and the assembly of making and the quality of galvanic couple are naturally not high yet.

The understanding that the present invention is based on the semiconductor refrigeration mechanism proposes a kind of new method for preparing refrigerating material and refrigeration device, it is characterized in that replacing with a kind of three-layer type composite construction refrigerating material the refrigerating material of present homogeneous texture.Described composite construction is comprised of the facing layer of two high α and the intermediate layer of a high σ, forms the sandwich of high α layer-high σ layer-high α layer, and transition between layers can suddenly change, and also can be gradual.Make first refrigerating material by this structure, then be cut into element, do top electrode, just obtain a kind of new cooling assembly.Can certainly directly prepare element by this structure, form new cooling assembly.The advantage of this composite construction can be passed through a N-N ⁺-N-type structure and a P-P ⁺-P-structure describes.If the N arm of thermoelectric couple and P arm have adopted respectively this two kinds of composite constructions, the α of two facing layer was high when then the thermoelectric couple energising was freezed, and the PERT effect is remarkable, and strong heat absorption capacity Q is arranged _cWith heat release ability Q _hMiddle N ⁺Layer and P ⁺The conductivity of layer is high, so Joule heat and produce the electrical power W that these Joule heats need to be paid _JJust very little.σ is high in addition, must cause the Seebeck coefficient α in intermediate layer _bVery low, overcome the required electrical power W that pays of thermoelectromotive force in intermediate layer _{Δ T}Also very little, so the gross electric capacity W=W that galvanic couple consumes _J+ W _{Δ T}Also inevitable very little, so, Energy Efficiency Ratio (being coefficient of refrigerating performance)

Can be very high.Can find out from this example, three-layer type composite construction and present homogeneous texture something in common are all to be made of refrigerating material, and difference is that composite construction is with the physical parameter of refrigerating material---and α, σ have done appropriate space with κ and have separated.The thin layer of each semiconductor refrigeration material is optimized the parameter configuration of oneself according to the physical action that oneself should play, outstanding main parameter, and then combining forms optimizing structure on the whole.Replace the single homogeneous texture of existing refrigerating material and refrigeration device with it, just broken through the technical bottleneck that conditions each other and cause between the single homogeneous texture parameter.Below we illustrate the performance advantage of this sandwich with a numeric example.Be easy to proof by the equation of heat balance under the stable state, adopt the galvanic couple of three layers structure, under maximum refrigeration work consumption operating mode, still have

$\mathrm{\Δ}{T}_{\max }=\frac{1}{2}{Z}_c{T^2}_{c\min },---\left(5\right)$

Wherein, Δ T _MaxBe maximum temperature difference, T _{C min}Minimum temperature during for the cold junction thermal insulation, Z _cBe the merit figue of galvanic couple under the three-layer composite structure, its size is,

α wherein _cBe the Seebeck coefficient of galvanic couple, α _c=| α _Cn|+α _CpBe the Seebeck coefficient summation of N-type facing layer and P type end side layer, R is the series connection all-in resistance of galvanic couple two arms, and K is the overall thermal conductance of galvanic couple two arm parallel connections.Because N-N ⁺-N structure and P-P ⁺Two facing layer are all thin a lot of than the intermediate layer in the-P-structure, so the value of R, K is determined by the intermediate layer basically.Get in the galvanic couple form factor under the condition of optimum value,

$Z_c=\frac{{{\mathrm{\α}}_c}^2}{{(\sqrt{{\mathrm{\κ}}_{\mathrm{bn}}{\mathrm{\ρ}}_{\mathrm{bn}}}+\sqrt{{\mathrm{\κ}}_{\mathrm{bp}}{\mathrm{\ρ}}_{\mathrm{bp}}})}^2}---\left(6\right)$

Wherein, footnote b represents the relevant parameter in intermediate layer, κ _Bn, κ _BpRespectively the intermediate layer thermal conductivity of N arm and the P arm of galvanic couple, ρ _Bn, ρ _BpRespectively the intermediate layer resistivity of N arm and the P arm of galvanic couple.

If in three layers structure, | α _Cn|=α _Cp=260 μ v/ ℃,

κ _Bn=κ _Bp=20x10 ^-3W/cm. ℃ then, Z _c=5.1x10 ^-3/ ℃.Adopt at present the tellurium bismuth alloy of homogeneous texture ^[7]Merit figue Z only be 2.5x10 ^-3/ ℃--3.0x10 ^-3/ ℃.As seen, the galvanic couple of employing three-layer type composite construction exceeds 70%--100% than the merit figue of the galvanic couple of homogeneous texture.Certainly, if only an arm is adopted the three-layer type composite construction in thermoelectric couple, another arm adopts traditional homogeneous texture, and then the degree improved of merit figue is so not high, improves or sure.The kind of semiconductor refrigeration material is a lot of in fact, wherein major part does not obtain application so far, the people that have its source in always use three large parameters of uniform blocks material as the standard of evaluating material quality, yet this standard is in fact also unreasonable, it makes us omit the material of many high-qualitys, such as, a kind of material Seebeck coefficient is originally very high, mix, it is very low that Seebeck coefficient becomes.This class material obviously is inferior material from traditional appraisal standards; But, if adopt above-mentioned three-layer type composite construction, then can produce very outstanding cooling assembly.On this meaning, the three-layer type composite construction makes semiconductor refrigeration material for us and cooling assembly has increased a kind of new thinking.

Reference:

【1】Majundar?A.“Thermoelectricity?in?Semiconductor?Nanostructures”，Science，2004，303：777-778

[2] thank Hua Qing, Xi Tonggeng " the hot physics of low-dimensional materials ", Science and Technology of Shanghai publishing house in September, 2008 front page

[3] " latest developments of Skutterudite thermoelectric material " material Leader such as Hu Anhui, 2007 year first phase

[4] Xu Guodong etc. " high merit figue thermoelectric material research ", material Leader, 2010 year third phase

[5] Luo Jun " thermoelectric material research ", in July, 2010 is in the thematic academic report of Chinese Academy of Sciences's CAS Institute of Physics

[6] Qian Youhua, Xu Zhizhong " Semiconductor Physics ", Higher Education Publishing House, in December, 2003

[7] Wang Jiqiang " chemical power source and physical power source ", National Defense Industry Press's second edition in 2008

Claims (3)

1. sandwich that is used for semiconductor refrigerating, comprise three refrigerating material thin layers, two superficial layers and an intermediate layer, transition between layers can suddenly change, also can be gradual, the Seebeck coefficient of superficial layer is high, the conductivity in intermediate layer is high, three-layered node forms composite construction altogether, it is characterized in that refrigerating material physical parameter-Seebeck coefficient, conductivity is separated with the space that thermal conductivity is done appropriateness, each refrigerating material thin layer is optimized the parameter configuration of self according to the physical action that self should rise, outstanding major parameter, then combining forms optimizing structure on the whole, breaks through the technical bottleneck of existing single even refrigerating material.

2. sandwich according to claim 1 is characterized in that described sandwich comprises by N-N ⁺-N structural composite material or P-P ⁺-P-structure composite material, wherein the Seebeck coefficient of two N-type superficial layers is high, middle N ⁺The conductivity of layer is high, or the Seebeck coefficient of two P type superficial layers is high, middle P ⁺The conductivity of layer is high.

According to claim 1 with sandwich claimed in claim 2, it is characterized in that directly preparing cooling module and cooling assembly according to this class composite construction.