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.

稀有地点的r_2s_3（r：la，ce，pr，nd，sm，eu，gd，tb，tb，dy，ho，yb和lu）通过稀有氧化物与CS_2气体的反应合成。除LU外，还获得了没有中间产品（例如氧硫化物）的合成粉末。在欧盟的情况下，获得了单硫化物。通过优化稀土金属与硫的比率，改善了热电特性。对于γ-GDS_X紧凑型，优异ZT的热电图随硫含量的减少而增加，并在x = 1.43时达到0.16。此外，测量了γ-LAS_ <1.5>紧凑型的热电性能，其晶体相通过在合成粉末中添加Ti来控制其晶体相。从四方β期到Y期的转化受氧杂质的影响。实际上，β期是硫化硫化物LA_ <10> s_ <14>（O_ <1-X> S_X），其0【小于或等于】x x x x x x x x x x y x x y y x x y y x <14>小于或等于或等于】1。尽管氧的存在稳定在较大温度范围内的四方形式，而低氧含量的β相在约1600 K左右的Y阶段进行了进一步的转化。我们观察到TI添加剂促进了从LA__ <10> s_ <10> s_ <14> o到γ-相位的转变。在8 wt的γ阶段中。％Ti，ZT随温度的增加，并在1000 K时达到0.21的值。Ti添加剂适合改善高温热电特性，因为它促进了具有高热电性能的Y期的形成。此外，带有Ti的β相是用于高温热电转化率的候选材料。 Seebeck核心的大小随温度而增加，而电阻降低。因此，ZT从300 K时的0.013突然增加到1000 K时的0.18。