Ca-Co-O熱電材料微波合成及其性能優(yōu)化
發(fā)布時間：2018-09-11 20:54
【摘要】：本文以Ca_9Co_(12)O_(28)熱電材料為研究對象,分別通過微波燒結(jié),摻雜與金屬復(fù)合等手段,改變熱電材料的晶界密度、載流子濃度和聲子散射中心數(shù)量,從而對其性能進(jìn)行優(yōu)化。實(shí)驗(yàn)研究成果如下:第一,采用微波燒結(jié)制備Ca_9Co_(12)O_(28)熱電材料,通過微波燒結(jié)過程中的晶粒細(xì)化效應(yīng),在本體材料中引入大量晶界,使得聲子的晶界散射幾率增大,降低了熱導(dǎo)率,最終實(shí)現(xiàn)熱電優(yōu)值的提高。實(shí)驗(yàn)結(jié)果表明經(jīng)微波燒結(jié)的樣品結(jié)構(gòu)更加致密,晶粒尺寸更小,平均尺寸在1um以下,其熱電優(yōu)值在500oC下達(dá)到0.042。第二,采用溶膠-凝膠法制備(Ca_(3-x)La_x)3Co_(12)O_(28)(x=0,0.05,0.1,0.15,0.2,0.3)熱電材料,通過在本體材料中摻雜稀土元素La,改變材料載流子濃度,從而引起熱電優(yōu)值的提高。實(shí)驗(yàn)發(fā)現(xiàn),(Ca2.9La0.1)3Co12O28的熱電優(yōu)值最高,在500oC時達(dá)到0.068,比未摻雜的Ca_9Co_(12)O_(28)提高約61.9%。表明摻雜稀土元素能有效提高材料的熱電性能。第三,采用化學(xué)溶液浸潤法制備(Ca_9Co_(12)O_(28))1-x Agx(x=0,0.005,0.01,0.015,0.02)熱電復(fù)合材料,使Ag均勻地分散在Ca-Co-O氧化物晶粒之間,形成有效的聲子散射中心,降低材料熱導(dǎo)率,提高其熱電優(yōu)值。通過性能測試在Ag復(fù)合比例為x=0.015的樣品ZT值最高,在500oC達(dá)到0.07,比純相提高約66.7%�？傊�,采用摻雜La方法可以改變材料載流子濃度,提高材料熱電性能;采用微波技術(shù)可以提高材料內(nèi)部晶界密度,降低了材料熱導(dǎo)系數(shù);采用Ag復(fù)合方法在材料內(nèi)部產(chǎn)生大量聲子散射中心,也可以有效降低材料熱導(dǎo)系數(shù)。從而為進(jìn)一步優(yōu)化熱電材料性能打下基礎(chǔ)。
[Abstract]:In this paper, Ca_9Co_ _ (12) O _ (28) thermoelectric materials are studied. By means of microwave sintering, doping and metal recombination, the grain boundary density, carrier concentration and the number of phonon scattering centers of thermoelectric materials are changed to optimize their properties. The experimental results are as follows: first, Ca_9Co_ _ (12) O _ (28) thermoelectric materials are prepared by microwave sintering. Through the grain refinement effect in the process of microwave sintering, a large number of grain boundaries are introduced into bulk materials, which increases the probability of phonon grain boundary scattering and reduces the thermal conductivity. Finally, the improvement of the excellent value of thermoelectricity is realized. The experimental results show that the microstructure of the samples sintered by microwave is denser, the grain size is smaller, the average size is below 1um, and the thermoelectric excellent value reaches 0.042 in 500oC. Secondly, (Ca_ (3-x) La_x) 3Co12 O28 (x00.05) 0.15 0.2ng) thermoelectric material was prepared by sol-gel method. The carrier concentration of the material was changed by doping rare earth element La, in bulk material, which resulted in the increase of thermoelectric excellent value. It is found that the thermoelectric excellent value of (Ca2.9La0.1) 3Co12O28 is the highest, reaching 0.068 at 500oC, which is 61.9% higher than that of undoped Ca_9Co_ _ (12) O _ (28). The results show that doped rare earth elements can effectively improve the thermoelectric properties of the materials. Thirdly, (Ca_9Co_ _ (12) O _ (28) 1-x Agx (XO _ 0. 005 ~ 0. 01 ~ 0. 015 ~ 0. 02) thermoelectric composites were prepared by chemical solution infiltration method. Ag was uniformly dispersed among Ca-Co-O oxide grains, forming effective phonon scattering centers, reducing the thermal conductivity of the materials and improving their thermoelectric excellence. The ZT value of the sample with Ag composite ratio of xn0. 015 is the highest, and the value of 500oC is 0. 07, which is about 66. 7% higher than that of pure phase. In a word, the carrier concentration of the material can be changed by doping La method, and the thermoelectric properties of the material can be improved, and the grain boundary density can be increased by microwave technology, and the thermal conductivity of the material can be reduced. A large number of phonon scattering centers are produced in the material by Ag composite method, which can also effectively reduce the thermal conductivity of the material. Thus lay the foundation for further optimizing the properties of thermoelectric materials.
【學(xué)位授予單位】：鄭州航空工業(yè)管理學(xué)院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB34
本文編號：2237813
[Abstract]:In this paper, Ca_9Co_ _ (12) O _ (28) thermoelectric materials are studied. By means of microwave sintering, doping and metal recombination, the grain boundary density, carrier concentration and the number of phonon scattering centers of thermoelectric materials are changed to optimize their properties. The experimental results are as follows: first, Ca_9Co_ _ (12) O _ (28) thermoelectric materials are prepared by microwave sintering. Through the grain refinement effect in the process of microwave sintering, a large number of grain boundaries are introduced into bulk materials, which increases the probability of phonon grain boundary scattering and reduces the thermal conductivity. Finally, the improvement of the excellent value of thermoelectricity is realized. The experimental results show that the microstructure of the samples sintered by microwave is denser, the grain size is smaller, the average size is below 1um, and the thermoelectric excellent value reaches 0.042 in 500oC. Secondly, (Ca_ (3-x) La_x) 3Co12 O28 (x00.05) 0.15 0.2ng) thermoelectric material was prepared by sol-gel method. The carrier concentration of the material was changed by doping rare earth element La, in bulk material, which resulted in the increase of thermoelectric excellent value. It is found that the thermoelectric excellent value of (Ca2.9La0.1) 3Co12O28 is the highest, reaching 0.068 at 500oC, which is 61.9% higher than that of undoped Ca_9Co_ _ (12) O _ (28). The results show that doped rare earth elements can effectively improve the thermoelectric properties of the materials. Thirdly, (Ca_9Co_ _ (12) O _ (28) 1-x Agx (XO _ 0. 005 ~ 0. 01 ~ 0. 015 ~ 0. 02) thermoelectric composites were prepared by chemical solution infiltration method. Ag was uniformly dispersed among Ca-Co-O oxide grains, forming effective phonon scattering centers, reducing the thermal conductivity of the materials and improving their thermoelectric excellence. The ZT value of the sample with Ag composite ratio of xn0. 015 is the highest, and the value of 500oC is 0. 07, which is about 66. 7% higher than that of pure phase. In a word, the carrier concentration of the material can be changed by doping La method, and the thermoelectric properties of the material can be improved, and the grain boundary density can be increased by microwave technology, and the thermal conductivity of the material can be reduced. A large number of phonon scattering centers are produced in the material by Ag composite method, which can also effectively reduce the thermal conductivity of the material. Thus lay the foundation for further optimizing the properties of thermoelectric materials.
【學(xué)位授予單位】：鄭州航空工業(yè)管理學(xué)院
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TB34
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