【摘要】：熱電材料可以實(shí)現(xiàn)熱能和電能直接轉(zhuǎn)換,在半導(dǎo)體電致冷和溫差發(fā)電領(lǐng)域有廣闊應(yīng)用前景。其性能由熱電優(yōu)值ZT值來衡量,高的ZT值要求材料具有低電阻率的同時具有高塞貝克系數(shù)和低熱導(dǎo)率。鈮酸鍶鋇具有特殊的鎢青銅結(jié)構(gòu),本征熱導(dǎo)率較低�？梢栽谄湮闯錆M的A_2位填充元素,調(diào)控電學(xué)性能,進(jìn)而優(yōu)化熱電性能。本論文的工作主要對鈮酸鍶鋇材料進(jìn)行堿金屬元素、稀土金屬元素填充,制備致密的Sr_(0.70)Ba_(0.30)M_xNb_2O_6陶瓷,研究不同燒結(jié)方法、不同填充元素、不同填充量等因素對材料熱電性能的影響。本論文取得的主要結(jié)果如下:一、對鈮酸鍶鋇材料填充堿金屬元素:(A)采用固相反應(yīng)法先空氣燒結(jié)再還原退火制備填充Li的樣品,填充量分別為x=0.01、0.03、0.05、0.08、0.10、0.15、0.20,制備得到單相致密的陶瓷。填充Li后,樣品電阻率降低,Seebeck系數(shù)絕對值也隨之降低。其中Sr_(0.70)Ba_(0.30)Li_(0.05)Nb_2O_6樣品電阻率最低,在1073K溫度時PF值達(dá)到486μW/K2m。但是填充Li后,樣品的熱導(dǎo)率略微升高,所以填充樣品ZT值提升不大。(B)直接在還原性氣體氛圍下燒結(jié)制備填充Li的樣品,PF值相對于先空氣燒結(jié)再還原退火制備的樣品偏低,熱電性能沒有得到優(yōu)化。二、對鈮酸鍶鋇材料填充稀土金屬元素:(A)填充Yb后,樣品電阻率降低,Sr_(0.70)Ba_(0.30)Yb_(0.10)Nb_2O_6樣品的電阻率最低,其PF值達(dá)到426 μW/K2m;填充Yb后樣品的熱導(dǎo)率降低,晶格熱導(dǎo)率相對于未填充樣品也略低,填充量越大熱導(dǎo)率越低,ZT值相對于未填充樣品有所提高,Sr_(0.70)Ba_(0.30)Yb_(0.05)Nb_2O_6樣品的ZT值在1073 K時達(dá)到0.21。(B)填充Y后,樣品電阻率降低,并且填充量越大電阻率越低,Sr_(0.70)Ba_(0.30)Y_(0.10)Nb_2O_6 樣品 PF 值達(dá)到 420μW/K2m,1073 K 時Sr_(0.70)Ba_(0.30)Y_(0.03)Nb_2O_6樣品的ZT值達(dá)到0.21。(C)填充量相同的情況下,填充Yb、Y稀土元素的樣品性能很相近。三、鈮酸鍶鋇材料填充K元素:實(shí)驗(yàn)表明,在還原性氣體氛圍下預(yù)燒可以提升最大填充量。在還原性氣體氛圍下預(yù)燒、燒結(jié)所得填充K樣品的電學(xué)性能優(yōu)于空氣燒結(jié)再還原退火制備的同填充量的樣品。Sr_(0.70)Ba_(0.30)K_(0.10)Nb_2O_6樣品PF值在1073 K時達(dá)到528 μW/K2m其ZT值達(dá)到0.23。本論文系統(tǒng)地研究了元素填充對鈮酸鍶鋇材料熱電性質(zhì)的影響,結(jié)果表明A位填充堿金屬元素或稀土金屬元素后,材料的電阻率和Seebeck系數(shù)絕對值降低,功率因子獲得提升。填充堿金屬元素后,材料功率因子提升較大,PF值可超過500μW/K2m;而填充稀土金屬后功率因子提升較低,最大值約為420μW/K2m。填充量較小時,材料的晶格熱導(dǎo)率高于未填充樣品,隨著填充量增大,晶格熱導(dǎo)率降低。填充堿金屬元素樣品的性能優(yōu)于填充稀土金屬元素樣品的性能,最高ZT值達(dá)到0.23。
[Abstract]:Thermoelectric materials can realize the direct conversion of thermal energy and electric energy, and have a broad application prospect in semiconductor electric cooling and thermoelectric power generation. Its performance is measured by the excellent value of ZT. The high value of ZT requires the material to have low resistivity and high Seebeck coefficient and low thermal conductivity. Barium strontium niobate has a special tungsten bronze structure and low intrinsic thermal conductivity. It is possible to fill the elements at the unfilled As _ 2 position to regulate the electrical properties and thus optimize the thermoelectric properties. The main work of this paper is to prepare dense Sr0.70 Ba0.30 MxNb2O6 ceramics by alkali metal elements and rare earth metal elements filled with strontium barium niobate. The effects of different sintering methods, different filling elements and different filling amount on the thermoelectric properties of the materials are studied. The main results obtained in this paper are as follows: firstly, the basic metal elements are filled with strontium barium niobate: (A) is used to prepare Li filled samples by air sintering and annealing by solid state reaction method. When Li is filled, the resistivity of the sample decreases and the absolute value of Seebeck coefficient decreases. Sr _ (0.70) Ba_ (0.30) Li _ (0.05) NB _ 2O _ 6 samples have the lowest resistivity, and the PF value reaches 486 渭 W / K _ 2 m at 1073K. However, the thermal conductivity of the samples increased slightly after Li was filled, so the ZT value of the filled samples was not much increased. (B) the PF value of the samples sintered directly in the atmosphere of reductive gas was lower than that of the samples prepared by air sintering and then reductive annealing. The thermoelectric performance is not optimized. Second, the rare earth metal elements filled with strontium barium niobate: after Yb was filled with (A), the resistivity of the sample decreased, Sr0.70 Ba0.30 Yb0.10 NbStud2O6 sample had the lowest resistivity, its PF value reached 426 渭 W / K2m.The thermal conductivity of Yb filled sample decreased and the lattice thermal conductivity was slightly lower than that of unfilled sample. The larger the filling amount, the lower the thermal conductivity, the lower the ZT value compared with the unfilled sample, the higher the ZT value of Sr0.70Ba0.30Yb0.05Nb2O6 sample is at 1073 K. (B) after filling Y, the resistivity of the sample decreases. Furthermore, the resistivity of Sr0.70 Ba0.30 Y0.10 Nb2O6 sample is lower than that of Sr0.70 Ba0.30Y0.10 Nb2O6 sample PF value of 420 渭 W / K2mt1073K, the ZT value of Sr0.70 Ba0.30 Y0.03 Nb2O6 sample is 0.21. (C) the properties of the rare-earth element filled with YbCY are very similar. Third, the material of strontium barium niobate is filled with K element: the experiment shows that pre-sintering in the atmosphere of reductive gas can increase the maximum filling amount. The electrical properties of sintered K samples prepared by pre-sintering in reductive gas atmosphere are better than those of the same filling amount samples. Sr0.70 Ba0.30 K0.10 Nb2O6 samples prepared by air sintering and rereduction annealing. The PF value of the sample reached 528 渭 W / K2m ZT value at 1073 K. The effect of element filling on the thermoelectric properties of strontium barium niobate is systematically studied in this paper. The results show that the resistivity and Seebeck coefficient of the material decrease and the power factor increases after filling the alkali or rare earth metal elements at the A site. After filling alkali metal element, the power factor of the material can increase more than 500 渭 W / K _ 2 m, but the power factor of the rare earth metal increases lower, the maximum value is 420 渭 W / K _ 2 m. The lattice thermal conductivity of the material is higher than that of the unfilled sample when the filling amount is small, and the lattice thermal conductivity decreases with the increase of the filling amount. The properties of the samples filled with alkali elements are better than those of the samples filled with rare earth metals, and the highest ZT value is 0.23.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TQ174.1

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