High-yield synthesis of semiconductive type-II Si clathrates with low Na content

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• 作者：Fumitaka Ohashi ; Masashi Hattori ; Takuya Ogura ; Yuzo Koketsu ; Roto Himeno ; Tetsuji Kume ; Takayuki Ban ; Tamio Iida ; Hitoe Habuchi ; Hironori Natsuhara ; Shuichi Nonomura
• 关键词：Si clathrate ; Guest free ; Semiconductor ; Thermal decomposition ; Synthesis mechanism
• 刊名：Journal of Non-Crystalline Solids
• 出版年：2012
• 出版时间：1 September, 2012
• 年：2012
• 卷：358
• 期：17
• 页码：2134-2137
• 全文大小：421 K

文摘

To develop an efficient synthesis of type-II Si clathrates with low Na content (Na_xSi₁₃₆: x = 0-24), various conditions for annealing the Zintl phase NaSi were examined. The addition of a pre-annealing process under vacuum at 250 ¡ãC following the preparation of NaSi resulted in a decrease in the Na content of type-II Si clathrates from 4 to 2 when the pre-annealing duration ranged from 0 to 60 h, while the volume fraction of type-II Si clathrate crystals in the synthesized specimens (type-II/(type-I + type-II + d-Si)) deduced by powder X-ray diffraction and Rietveld analysis was maintained at approximately 85 % . These preparation techniques that enable the high-yield synthesis of semiconductive type-II Si clathrates open opportunities for the application of these substances to semiconductor devices.