本文選題：n型Bi2Te3基熱電材料　切入點(diǎn)：燒結(jié)　出處：《哈爾濱師范大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：熱電材料是一種可以實(shí)現(xiàn)電能和熱能相互轉(zhuǎn)化的功能材料,有關(guān)塞貝克效應(yīng)與帕爾貼效應(yīng)的研究為熱電材料的廣泛應(yīng)用提供了堅(jiān)實(shí)的理論基礎(chǔ)。熱電器件普遍具有體積小,質(zhì)量輕,無污染,可回收和易控制等優(yōu)點(diǎn)。然而,由熱電材料制造的裝置(如冰箱等)工作效率卻低于傳統(tǒng)工作方式(如壓縮機(jī)制冷)。通常使用熱電優(yōu)值Z值來評價材料的熱電效率,Z值越高,說明材料熱電效率越高。因此,如何提升Z值,成為熱電材料研究領(lǐng)域的一個核心問題。Bi2Te3基熱電材料是當(dāng)前熱電材料研究領(lǐng)域中最為熱門的材料之一,由于其熱電性能好,因而在半導(dǎo)體元器件制作中得到了廣泛應(yīng)用。本文以n型Bi2Te3基贗三元熱電材料為研究對象,采用單質(zhì)熔煉化合法制得n型Bi2Te3固溶體合金。并通過碳纖維摻雜,得到n型贗三元碳纖維摻雜Bi2Te3復(fù)合材料粉體。通過熱壓燒結(jié)法獲得n型贗三元碳纖維摻雜Bi2Te3復(fù)合塊體材料。在惰性氣體環(huán)境下燒結(jié),針對不同燒結(jié)溫度的n型碳纖維摻雜Bi2Te3復(fù)合材料塊體進(jìn)行熱電性能及微觀結(jié)構(gòu)分析。經(jīng)過微觀結(jié)構(gòu)分析結(jié)果表明,通過對樣品進(jìn)行SEM和XRD處理,發(fā)現(xiàn)碳纖維在n型Bi2Te3基贗三元熱電材料中分布均勻,并且起到了較為明顯的連接作用,高溫?zé)Y(jié)使n型Bi2Te3基贗三元熱電材料的結(jié)構(gòu)更加緊湊,使原來分散的晶粒結(jié)構(gòu)能夠融合在一起,成為較大的晶粒;整體結(jié)構(gòu)也由原來較為松散的無規(guī)則形狀,經(jīng)燒結(jié)成為了明顯的梯田狀結(jié)構(gòu),增強(qiáng)了材料的熱電性能,對于材料Z值的提升是有積極意義的;載流子疏運(yùn)分析結(jié)果表明,在一定溫度范圍內(nèi),載流子的遷移率和濃度都隨著燒結(jié)溫度的升高而升高;熱電性能分析結(jié)果表明,熱壓溫度恒定的情況下,隨著燒結(jié)溫度的升高,n型碳纖維摻雜Bi2Te3復(fù)合材料的熱導(dǎo)率κ呈現(xiàn)出先減小后增大的趨勢,并且在燒結(jié)溫度達(dá)到約300℃的時候達(dá)到最大值;電導(dǎo)率σ呈現(xiàn)出先減小后升高的趨勢,并且在燒結(jié)溫度達(dá)到250℃的時候達(dá)到最小值;n型碳纖維摻雜Bi2Te3復(fù)合材料的塞貝克系數(shù)α呈現(xiàn)先增大后減小的趨勢,在燒結(jié)溫度達(dá)到300℃的時候達(dá)到最大值。最后經(jīng)過計(jì)算得到熱電優(yōu)值表明,在低溫區(qū),n型Bi2Te3基贗三元碳纖維摻雜復(fù)合熱電材料隨著燒結(jié)溫度的升高,熱電優(yōu)值呈現(xiàn)出遞增趨勢,并且在300℃達(dá)到最大值,這也證明了300℃為低溫區(qū)本實(shí)驗(yàn)原料的最佳燒結(jié)溫度。綜上所述,本文通過微觀結(jié)構(gòu)分析、載流子輸運(yùn)結(jié)果分析和熱電性能分析等手段,采用了SEM、XRD、高溫?zé)Y(jié)等手段,預(yù)測了燒結(jié)溫度與n型Bi2Te3基贗三元碳纖維摻雜復(fù)合熱電材料性能的關(guān)系。通過研究獲得了贗三元材料的最佳燒結(jié)溫度和熱電性能隨著燒結(jié)溫度變化的基本規(guī)律,揭示了燒結(jié)溫度對材料熱電性能影響的機(jī)理。研究結(jié)果對于進(jìn)一步研究贗三元熱電材料性能具有重要意義。
[Abstract]:Thermoelectric material is a kind of functional material which can realize the mutual conversion of electric energy and heat energy. The research on Seebeck effect and Partil effect provides a solid theoretical basis for the wide application of thermoelectric materials. Thermoelectric devices are generally small in size. Light weight, pollution-free, recyclable and easy to control. However, The working efficiency of devices made of thermoelectric materials (such as refrigerators, etc.) is lower than that of conventional working methods (such as compressor refrigeration). The higher the thermoelectric efficiency (Z value) is usually used to evaluate the thermoelectric efficiency (Z value) of materials, the higher the thermoelectric efficiency of materials is. How to raise Z value has become a core problem in the field of thermoelectric material research. Bi2Te3-based thermoelectric material is one of the most popular materials in the field of thermoelectric material research at present, because of its good thermoelectric properties, In this paper, n-type Bi2Te3 based pseudo-ternary thermoelectric material was used as the object of study. N type Bi2Te3 solid solution alloy was prepared by simple melting and combining method, and doped with carbon fiber. N type pseudo ternary carbon fiber doped Bi2Te3 composite powder was obtained. N type pseudo ternary carbon fiber doped Bi2Te3 bulk material was obtained by hot pressing sintering. The thermoelectric properties and microstructure of n-type carbon fiber doped Bi2Te3 composites with different sintering temperatures were analyzed. The results of microstructure analysis showed that the samples were treated with SEM and XRD. It is found that carbon fiber distributes uniformly in n-type Bi2Te3 based pseudo-ternary thermoelectric materials and plays a more obvious connection role. The structure of n-type Bi2Te3 based pseudo-ternary thermoelectric materials is more compact by high temperature sintering. The original dispersed grain structure can be fused together to become larger grain. The whole structure is also changed from the original loose irregular shape to a clear terraced structure after sintering, which enhances the thermoelectric properties of the material. The results of carrier transport analysis show that the mobility and concentration of carriers increase with the increase of sintering temperature, and the results of thermoelectric properties analysis show that the carrier transport rate and concentration increase with the increase of sintering temperature. When the hot pressing temperature is constant, the thermal conductivity 魏 of n-type carbon fiber doped Bi2Te3 composites decreases first and then increases with the increase of sintering temperature, and reaches the maximum value when sintering temperature reaches about 300 鈩，

本文編號：1631956