ZnO基热电材料的掺杂改性及微结构调控

发布时间：2018-04-23 22:11

本文选题：ZnO + 热电　；参考：《北京科技大学》2017年博士论文

【摘要】：热电材料在废热发电、空调及冰箱制冷等领域具有广阔的应用前景,近年来受到了越来越大的关注。氧化物热电材料具有抗氧化、耐高温、并且无污染、无毒性、制备工艺简单等特点,在中高温热电应用领域具有很大的应用潜力。本论文着眼于n型氧化锌(ZnO)热电材料,采用固相反应法(SSR)和水热合成(HS)法制备化合物前驱粉体,采用放电等离子烧结法(SPS)制备多晶块体材料,并通过Al、Ni、Ga等元素掺杂改性优化载流子浓度,通过织构化与纳微复合结构化设计优化载流子迁移率、降低热导率,达到优化ZnO热电性能目的。在不同的烧结温度1173-1323K的条件下,通过SSR结合SPS技术制备了致密并且晶粒较小的Zn0.96Al0.04O块体材料。随着烧结温度的增加,ZnAl2O4第二相含量逐渐增加。1223K时烧结样品在823K时取得最大功率因子4.01×10~(-4)Wm-1K-2。1173K时烧结样品因其较小的晶粒尺寸及ZnAl2O4第二相的偏析,在773K时取得较低热导率2.42Wm-1K-1及最优ZT值0.11。通过HS和SPS技术制备了织构化Al掺杂Zn_(1-x)AlxO(x=0,0.01,0.02,0.04)块体。块体样品获得了～0.6的织构度,因水热过程中高的PH值8.5-9.0,A13+的固溶度较低,同时并未检测到ZnAl2O4第二相。织构样品容易获得较高的电子迁移率,随着测试温度由373K增加至573K, Zn0.96Al0.04O样品的电导率由68.2Scm-1增加至749.2Scm-1。最终,Zn0.96Al0.04O样品在573K时取得最.大功率因子4.7x 10~(-4)Wm-1K-2。通过HS和SPS技术制备了织构化Al、Ni共掺杂Zn0.98-xAl0.02NixO(x=0,0.01,0.02,0.03,0.04)块体。共掺杂的Ni2+在水热过程中更易进入ZnO晶胞间隙位置并膨胀晶胞,导致粉体及块体中A13+固溶度大幅度提升,并获得较高的载流子浓度～1×1020cm-3。高的A13+固溶度及高的迁移率导致Zn0.97Al0.02Ni0.01O样品在673K时取得最大功率因子6.16×10~(-4)Wm-1K-2,并在773K时取得最优ZT值0.057。通过HS和SPS技术制备了纳微复合结构的Zn_(1-x)GaxO(x=0,0.01,0.02,0.04)块体。样品获得了较高的Ga3+固溶度,还获得较高的载流子迁移率。x=0.01样品,在773K时取得最大功率因子7.52x10~(-4)Wm-1K-2。粉体纳微复合结构在块体中的被保持,样品获得了较小的晶粒,增加了声子的散射,减小了热导率。x=0.04样品,773K时取得最低热导率5.15Wm-1K-1。x=0.02样品,773K时取得最大ZT值0.067。通过HS和SPS技术制备了纳微复合结构的Zn_(1-x)AlxO(x=0,0.02,0.03,0.04)块体。纳微复合结构样品因存在纳米共格晶界导致其获得较高的载流子迁移率的同时降低热导率。x=0.02样品常温下获得了最高的载流子迁移率50.7cm2V-1s-1和载流子浓度1.5×1020cm-3,该样品的载流子迁移率已接近单晶的迁移率。x=0.04样品在1073K时取得最低热导率1.60Wm-1K-1。x=0.02样品在1073K时取得最优ZT值0.36。通过HS和SPS技术制备了C掺杂ZnO热电陶瓷。作为C源的TEA在SPS过程中,电离出C~(x+)和Cx-,进入ZnO晶胞。相比于未掺杂ZnO样品,C掺杂ZnO样品的可见光光吸收增加,禁带宽度减小,功率因子提升约1.5倍。
[Abstract]:Thermoelectric materials have wide application prospects in waste heat generation, air conditioning and refrigerator refrigeration, etc. In recent years, more and more attention has been paid to thermoelectric materials. Oxide thermoelectric materials have many advantages, such as oxidation resistance, high temperature resistance, no pollution, no toxicity, simple preparation process and so on, so they have great application potential in the field of medium and high temperature thermoelectric applications. In this paper, the precursor powder of compound was prepared by solid state reaction method (SSRs) and hydrothermal synthesis (HSS) method, and the polycrystalline bulk material was prepared by spark plasma sintering (SPS) method. The carrier concentration was optimized by doping Al _ 2O _ 3 and Ni _ 2O _ Ga, the carrier mobility was optimized by texturing and nanocomposite structured design, the thermal conductivity was reduced, and the thermoelectric properties of ZnO were optimized. At different sintering temperatures of 1173-1323K, compact and smaller Zn0.96Al0.04O bulk materials were prepared by SSR and SPS technique. With the increase of sintering temperature, the second phase content of ZnAl _ 2O _ 4 increases gradually. At 823K, the sintered sample obtains the maximum power factor 4.01 脳 10~(-4)Wm-1K-2.1173K, because of its smaller grain size and segregation of the second phase of ZnAl2O4, the lower thermal conductivity 2.42Wm-1K-1 and the optimum ZT value 0.11 are obtained at 773K. The textured Al-doped ZnSZ 1-xOXOXOXOXOX 00.01OXOXOXOX (00.01) bulk was prepared by means of HS and SPS techniques. The bulk samples obtained a texture of 0. 6, and the high PH value of 8. 5-9. 0 A _ (13) in hydrothermal process was relatively low, and the second phase of ZnAl2O4 was not detected at the same time. It is easy to obtain high electron mobility for textured samples. With the increase of testing temperature from 373K to 573K, the conductivity of Zn0.96Al0.04O samples increases from 68.2Scm-1 to 749.2Scm-1. The final Zn0.96Al0.04O sample was obtained at 573K. High power factor 4.7x 10 ~ (-4) W ~ (m-1K ~ (-2)). Co-doped Zn0.98-xAl0.02NixOOXOXOOXOOXOXOOXOXO (0. 01 ~ 0. 01 ~ 0. 02 ~ 0. 03 ~ 0. 04) bulk with textured Alnu Ni was prepared by means of HS and SPS techniques. It is easier for co-doped Ni2 to enter the intercellular gap of ZnO and expand the cell during hydrothermal process, which leads to a large increase in the solid solubility of A13 in powders and bulk, and a higher carrier concentration of 1 脳 1020cm-3. The high solubility of A13 and high mobility resulted in the maximum power factor of 6.16 脳 10 ~ (-4) Wm-1K-2 at 673K and the optimal ZT value of 0.057 at 773K. The nanocomposite ZnS _ (1-x) _ (x) _ (x) _ (0. 01) ~ (0. 02) ~ (0.04) bulk was prepared by means of HS and SPS techniques. The sample obtained higher Ga3 solid solubility and higher carrier mobility. At 773K, the maximum power factor of 7.52x10m-1 K-2 was obtained. The nanocrystalline nanocomposite structure was kept in the bulk, and the sample obtained smaller grain size, increased phonon scattering, and reduced the thermal conductivity of the sample at 773K. The maximum ZT value was 0.067 when the lowest thermal conductivity of 5.15Wm-1K-1.x=0.02 sample was obtained at 773K. The nanocomposite ZnS _ (1-x) Al _ (x) O _ (x) O _ (00.02) O _ (0.03) _ (0.04) bulk has been prepared by HS and SPS techniques. The nanocrystalline composite structure samples obtained high carrier mobility due to the existence of nanoscale lattice grain boundaries and decreased the thermal conductivity. X0. 02. The highest carrier mobility 50.7cm2V-1s-1 and carrier concentration 1.5 脳 1020cm-3 were obtained at room temperature. The mobility of streamon is close to that of single crystal. X0. 04 samples obtain the lowest thermal conductivity at 1073 K. The optimal ZT value of 1.60Wm-1K-1.x=0.02 sample at 1073 K is 0.36. C-doped ZnO thermoelectric ceramics were prepared by HS and SPS techniques. TEA, as a C source, ionizes CX and Cx-in the SPS process and enters the ZnO cell. Compared with the undoped ZnO samples, the visible light absorption of C doped ZnO samples increased, the band gap decreased and the power factor increased about 1.5 times.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ174.1

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