The Study on the Modification of FeSe with Isostructural LiOH

• Main Authors: Wei-HsinLiu, 劉煒薪
• Other Authors: Xiao-ding Qi
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/03716965244598180275

碩士 === 國立成功大學 === 材料科學及工程學系 === 103 === This work attempts to modify the PbO-type iron selenide (i.e. the β-phase FeSe) with the isostructural lithium hydroxide (LiOH). It is expected that LiOH may form a solid solution with FeSe under proper thermodynamic conditions and therefore, result in some changes in the superconducting properties of FeSe. The experimental parameters, such as composition, temperature, pressure and heating time, were varied to find the desired phase region. The FeSe-LiOH solid solution containing up to 17 mol% LiOH was formed after sintering at 300 ℃ under 0.75 GPa for 24 hrs, followed by annealing at 160 ℃ under 0.75 GPa for 12 hrs. However, the critical temperature (Tc) was only increased by about 2 K, which reached 10.7 K in the 0.83 FeSe-0.17 LiOH samples. As the LiOH content increased, a new phase was formed, which had the composition (Li0.4Fe0.6)OHFeSe. The new phase showed a possible Tc of 33 K, much higher than the FeSe-LiOH solid solution. The suitable pressure for the formation of the new phase was within the range between 0.75 to 1 GPa, but the accurate phase region for the composition and temperature has yet to be clarified as our samples still contained some other secondary phases.