化学气相沉积法制备无无机热电纤维

PREPARATION OF INORGANIC THERMOELECTRIC FIBERS BY CHEMICAL VAPOR DEPOSITION

胡继真

11649156

硕士

材料工程

刘玮书

2018-06-04

2018-06-25

哈尔滨工业大学

深圳

近年来，物联网技术正在全球推动着一轮新的科技革命，期待从环境热能中获取电能并独立工作的传感器终端对传统的热电器件提出了微型化需求。本论文成功地化学气相沉积（CVD）法制备出 Bi2S3 等多种无机热电纤维，该纤维未来有望简化微型热电器件的封装工艺。本论文发现一种基于封闭的 CVD 系统生长无机热电晶须的简单方法，该系统包含一个垂直放置在立式管式炉的玻璃管，原料在高温下熔化并形成金属蒸汽，金属原子蒸发并在玻璃管的低温度区形核并长成晶须，该方法单次可以获得超过 1000 根长度为 2-9 mm 的晶须。此 CVD 法被成功地应用于生长 Bi2S3, Bi2Te3，Sb2Te3，Bi2SeS2，SnS 等具有各项异性晶体结构的晶须，具有一定的通用性。研究发现，S 蒸汽对晶须的形成具有关键作用，对于不含硫的 Bi2Te3 和 Sb2Te3 需要加入至少 5 wt.% S 才能获得晶须。通过对 Bi2S3 和 Bi2Te3 的晶须生长进行系统研究，发现晶须的形貌与熔体的温度有很大关联，适合晶须生长的熔池温度区间为 800-1000 oC。此外，我们还利用该系统获得具有立方结构的 PbS 晶须。本文还系统研究了三元系统的 Bi2S3-mSem 晶须成分精准控制。由于 S 和Se 蒸汽压的不同，晶须中的 S/Se 的比例与熔池中的成份不同。本文选取 5 个不同化学计量比的 Bi2S3-mSem熔体在 900 oC 下获得晶须，利用 EDS 分析成分，获得晶须成分与原料成分的关系，并通过实验进行了验证。然后，本文对 Bi2S3- mSem 三元体系的晶须的热电性能进行了研究。经过 Cu 掺杂后，化学计量比Cu0.01Bi2SeS2 原料所得晶须的电阻率降低了一个数量级，Seebeck 系数略微降低，最终功率因子提升了四倍，达到 450~480 μW·m-1·K-2，和块体 Cu0.01Bi2SeS2材料相当。进行 Cl 掺杂，化学计量比 Cl0.01Bi2SeS2 原料所得晶须的功率因子最高达到 1480 μW·m-1·K-2。本文所发展的封闭式 CVD 晶须成长方法简单实用，且具有通用性。未来我们将进一步依托该方法获得晶须，进一步封装制备出相应的微型热电器件，并应用于从环境中获取电能

In recent years, the Internet of Things is propelling a new revolution in science and technology globally. It is expected that sensor terminals that can obtain electrical energy from environmental heat independently will put forward a demand for the miniaturization of traditional thermoelectric devices. In this dissertation, wesuccessfully prepared Bi2S3 and other inorganic thermoelectric fibers by chemical vapor deposition (CVD). Those fibers are expected to simplify the packaging process of micro thermoelectric devices in the future.The paper found a simple method for growing inorganic thermoelectric whiskers based on a closed CVD system. The system consists of a glass tube placed vertically in a vertical tube furnace. The raw material melts at high temperature and becomes metal vapor. The metal atoms evaporate, nucleate and grow into whiskersin the low temperature region of the glass tube. This method can obtain more than 1000 whiskers with a length of 2-9 mm in a single shot. The CVD method with versatility has been successfully applied to the growth of Bi 2S3, Bi2Te3, Sb2Te3, Bi2SeS2, SnS and other crystal whiskers with anisotropic crystal structure. It has been found that S-vapor plays a key role in the formation of whiskers. For sulfur_x005ffree Bi2Te3 and Sb2Te3, at least 5 wt.% S is required to obtain whiskers. A systematic study of the whisker growth of Bi2S3 and Bi2Te3 shows that the morphology of the whiskers is closely related to the temperature of the melt. The temperature range of the molten pool suitable for whisker growth is 800-1000 oC. In addition, we also used this system to obtain PbS whiskers with a cubic structure.This article also systematically studied the precise control of the Bi 2S3-mSemwhisker composition of the ternary system. Due to the difference in vapor pressures of S and Se, the ratio of S/Se in whiskers is different from that in the melt. In the paper, five different stoichiometric ratios of Bi2S3-mSem melts were used to obtain whiskers at 900 oC. Using EDS to analyze components, the relationship between whisker components and raw material compositions was obtained and verified by experiments. Next, the thermoelectric properties of the whiskers of the Bi 2S3-mSemternary system were studied. After Cu doping, the resistivity of the whisker obtained from stoichiometric Cu0.01Bi2SeS2 material is reduced by an order of magnitude, the Seebeck coefficient is slightly reduced, and the final power factor is increased four times to 450-480 μW·m-1·K-2, which is comparable with bulk Cu0.01Bi2SeS2material. With Cl doping, the whisker with the stoichiometric ratio Cl0.01Bi2SeS2has a power factor of 1480 μW·m-1·K-2.The closed CVD whisker growth method developed in the paper is simple, practical and versatile. In the future, we will further use this method to obtain whiskers, further encapsulate and prepare corresponding miniature thermoelectric devices, and apply them to obtaining electrical energy from the environment.

CVD 晶须 Bi2SeS2 热电性能

CVD Whisker Bi2SeS2 Thermoelectric performance

中文

联合培养

南方科技大学

胡继真. 化学气相沉积法制备无无机热电纤维[D]. 深圳. 哈尔滨工业大学,2018.