Development of lanthanoid sulfides for ceramics condenser with large-capacity

大容量陶瓷电容器用镧系元素硫化物的研制

基本信息

批准号：
16360369
负责人：
HIRAI Shinji
金额：
$ 9.15万
依托单位：
Muroran Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

Rare-earth sesquisulfides R_2S_3 (R : La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb, and Lu) were synthesized by the reaction of rare-earth oxides with CS_2 gas. With the exception of Lu, synthetic powders devoid of intermediate products such as an oxysulfide were obtained. A monosulfide was obtained in the case of Eu. The thermoelectric properties were improved by the optimization of the ratios of rare-earth metal to sulfur. For a γ-GdS_x compact, the thermoelectric figure of merit ZT increased with a decrease in the sulfur content and reached a value of 0.16 at x = 1.43. Moreover, the thermoelectric properties were measured for the γ-LaS_<1.5> compact whose crystal phase was controlled by the addition of Ti to a synthetic powder. The transformation from the tetragonal β-phase to the y-phase is affected by the oxygen impurities. The β-phase is in fact an oxysulfide La_<10>S_<14>(O_<1-x>S_x) with 0【less than or equal】x【less than or equal】1. While the presence of oxygen stabilizes the tetragonal form over a wide temperature range, the β-phase with a low oxygen content undergoes further transformation to the y-phase at around 1600 K. We observe that the Ti additive promotes the transformation from La_<10>S_<14>O to the γ-phase. In the γ-phase with 8 wt. % Ti, ZT increases with the temperature and reaches a value of 0.21 at 1000 K. The Ti additive is suitable for improving the high-temperature thermoelectric properties because it promotes the formation of the y-phase with high thermoelectric performance. Moreover, the β-phase with Ti is a candidate material for high-temperature thermoelectric conversion. The magnitude of the Seebeck coefficient increases with the temperature, while the electrical resistivity decreases. Consequently, ZT increases abruptly from 0.013 at 300 K to 0.18 at 1000 K.

稀土倍半硫化物R_2S_3（R：La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Yb和Lu）是通过稀土氧化物与CS_2气体反应合成的。在使用 Lu 的情况下，获得了不含硫氧化物等中间产物的合成粉末。热电性能得到了改善。稀土金属与硫的比例的优化对于γ-GdS_x压块，热电品质因数ZT随着硫含量的减少而增加，并且在x=1.43时达到0.16的值。通过向合成粉末中添加Ti来控制其晶相的γ-LaS_<1.5>压坯从四方β相的转变。 y相受氧杂质影响，β相实际上是氧硫化物La_<10>S_<14>(O_<1-x>S_x)，0【小于等于】x【小于等于）。】1. 虽然氧的存在可以在很宽的温度范围内稳定四方晶系，但氧含量较低的 β 相在 1600 K 左右会进一步转变为 y 相。我们观察到Ti添加剂促进了La_10S_14O向γ相的转变，在Ti含量为8wt％的γ相中，ZT随温度升高而增加，并在1000K时达到0.21。添加剂适合于改善高温热电性能，因为它促进了具有高热电性能的 y 相的形成，此外，含有 Ti 的 β 相是一种候选材料。高温热电转换。塞贝克系数的大小随着温度的升高而增加，而电阻率则降低，ZT 从 300 K 时的 0.013 突然增加到 1000 K 时的 0.18。