本文關(guān)鍵詞： 熱電性能 摻雜 Ti_(1-x)Nb_xO_2-d Magnéli相 TinO_2n-1　出處：《河北師范大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著人類社會(huì)的發(fā)展,煤、石油、天然氣等不可再生能源逐漸枯竭,這些能源的使用導(dǎo)致了全球變暖,進(jìn)而導(dǎo)致沙漠化區(qū)域逐漸增大以及海平面的上升,這使得新能源的探索和開發(fā)工作變得越來越重要,而要真正地使用新能源則必須借助于新能源材料。熱電材料屬于一種新能源材料,它可以直接將廢熱轉(zhuǎn)化為電能而不會(huì)造成環(huán)境污染,是一種綠色可持續(xù)能源材料。熱電轉(zhuǎn)換作為傳統(tǒng)發(fā)電技術(shù)的有效補(bǔ)充,得到人們?cè)絹碓蕉嗟年P(guān)注。熱電材料目前面臨的最大挑戰(zhàn)是其能量轉(zhuǎn)換效率在很大程度上尚未達(dá)到實(shí)際應(yīng)用的需要。為了使熱電材料得到更加廣泛的應(yīng)用,科研工作者嘗試通過摻雜等方式來提高材料的熱電性能。本論文選取氧化物半導(dǎo)體熱電材料TiO_2作為研究對(duì)象,對(duì)其進(jìn)行Nb元素?fù)诫s,并進(jìn)行了不同還原條件的熱處理,然后研究了Nb元素?fù)诫s和不同的還原條件處理對(duì)系列樣品的熱電性能的影響。本文的具體工作如下:1、使用傳統(tǒng)的固相反應(yīng)法,通過在1473 K,H2/Ar混合氣氛中進(jìn)行還原處理,制備了不同Nb含量的Ti_(1-x)Nb_xO_2-d系列陶瓷樣品。XRD圖譜顯示,x=0.0,0.005,0.01樣品表現(xiàn)為混合的三斜相TinO_2n-1結(jié)構(gòu)(8≤n≤10),而x=0.04,0.08樣品表現(xiàn)為單一的金紅石型TiO_2結(jié)構(gòu),這表明較高的Nb摻入量可以穩(wěn)定TiO_2的金紅石結(jié)構(gòu)。在最高測(cè)試溫度380 K,x=0.01樣品給出該系列樣品的最大ZT值0.023,這一數(shù)值大約是x=0.0未摻雜樣品ZT值(0.009)的2.6倍。在室溫到380 K范圍,該系列樣品的輸運(yùn)行為滿足小極化子導(dǎo)電機(jī)制。2、使用固相反應(yīng)法在高溫(1573 K)還原性氣氛(H2)中制備了不同Nb摻雜量的Ti_(1-x)Nb_x O_2-d系列陶瓷樣品。粉末XRD結(jié)果顯示:x=0.0,0.01,0.02和0.04樣品表現(xiàn)為混合的三斜相TinO_2n-1結(jié)構(gòu)(4≤n≤6),在x=0.08,0.20樣品中出現(xiàn)了四方相金紅石型TiO_2的衍射峰,而x=0.40,0.60樣品表現(xiàn)為單一的金紅石型結(jié)構(gòu),這表明較高濃度的Nb摻雜,可以使TiO_2的金紅石型結(jié)構(gòu)穩(wěn)定存在。在100-380K的溫度范圍,測(cè)試了該系列樣品的熱電性能。測(cè)試結(jié)果表明,樣品的電阻率和塞貝克系數(shù)隨溫度的變化都表現(xiàn)為半導(dǎo)體行為。通過分析證明了樣品在室溫到380 K溫區(qū)的輸運(yùn)行為滿足小極化子導(dǎo)電機(jī)制。在最高測(cè)試溫度380 K,x=0.20樣品給出該系列樣品的最大ZT值0.016。3、使用PLD方法在襯底溫度為550℃,激光能量密度為5 J/cm2,沉積頻率為2 Hz,氧壓為1.0×10-2 Pa的條件下,在(0001)取向的單晶Al2O3襯底上外延生長(zhǎng)了119 nm厚度的TiO_2薄膜。由XRD圖譜可看出,制備的薄膜為(l00)取向的金紅石型TiO_2薄膜,(200)和(400)晶面衍射峰分別出現(xiàn)在39.13°和84.25°。在室溫下,測(cè)量了金紅石TiO_2薄膜的電阻率和塞貝克系數(shù),四探針法測(cè)試結(jié)果給出該薄膜的室溫電阻率為130 mΩ·cm,其塞貝克系數(shù)為-55μV/K,計(jì)算得到金紅石TiO_2薄膜樣品室溫時(shí)的功率因子為0.0023 mW/(m·K2)。
[Abstract]:With the development of human society, non-renewable energy sources, such as coal, oil and natural gas, are gradually exhausted. The use of these sources of energy leads to global warming, which in turn leads to the gradual enlargement of desertification areas and the rise of sea level. This makes the exploration and development of new energy more and more important, and the real use of new energy has to rely on new energy materials. Thermoelectric materials are a kind of new energy materials. It can directly convert waste heat into electric energy without environmental pollution. It is a green and sustainable energy material. Thermoelectric conversion is an effective supplement to traditional power generation technology. The biggest challenge of thermoelectric materials is that their energy conversion efficiency has not met the needs of practical application to a great extent. In order to make thermoelectric materials more widely used, In this paper, the oxide semiconductor thermoelectric material (TiO_2) is chosen as the research object, which is doped with NB element and heat treated under different reduction conditions. Then the effects of NB doping and different reduction conditions on the thermoelectric properties of the series samples were studied. The specific work of this paper is as follows: 1, using the traditional solid state reaction method, the reduction treatment is carried out in the mixed atmosphere of 1473 Ku H2 / ar. The samples of Ti_(1-x)Nb_xO_2-d series with different NB contents were prepared. The results showed that the samples showed mixed triclinic phase TinO_2n-1 structure (8 鈮，

本文編號(hào)：1502070