High pressure synthesis and physical properties of rare earth borides with a cage like

本研究的目的是以RB_6和RB_<12> (R=La ~ Yb)稀土硼化物为原料，采用高压合成技术（最高压力= 10GPa，最高温度=1800℃）合成目前在环境压力下无法合成的材料。利用光谱学方法对金属的磁性、输运性、热学性质和电子结构进行测量，有望发现价涨落、近藤效应、近藤半导体、多极有序和新磁有序等许多有趣的行为。研究代表Iga介绍了一种最高温度1800℃、最高压力4GPa条件下的台式高压合成设备。Iga试图用高压合成GdB_<12>。高压合成的最佳条件尚未确定。另外，该设备可用于笼形物和角脱石化合物的合成。Iga和合作者yamanaka教授尝试在5GPa的压力下，在1600℃条件下，在约1小时的条件下，利用立方体积的设备进行GdB_<12>的高压合成。x射线分析表明，GdB_6和GdB_<12>两相以1:1的比例形成。此外，我们在去年尝试了在10GPa和1500℃下的高压合成。为了得到GdB_<12>的单相，在立方双相中加入了八面体双相。这种方法是山中教授发明的。目前还在不断寻找较好的条件。

The purpose of this research is synthesis of materials that cannot be synthesized up to now under ambient pressure by the technique of a high-pressure synthesis (highest pressure= 10GPa, maximum temperature=1800℃) among rare earth borides of RB_6 and RB_<12> (R=La〜Yb). Many interesting behaviors such as valence fluctuation, Kondo effect, Kondo semiconductor, multipole ordering and new magnetic ordering will be expected to be found from the measurements of magnetism, transport, thermal properties, and the electronic structure by the optical spectroscopy.Research representative's Iga introduced a desk-top type high-pressure synthetic equipment under the condition of the maximum temperature 1800℃ and highest pressure 4GPa. Iga tried to do a high-pressure synthesis of GdB_<12>. The optimum condition for high pressure synthesis is not yet established. Otherwise, this equipment is useful for synthesis of clathrate and skutterdite compounds.Iga and the research collaborator Prof.Yamanaka tried to do a high pressure synthesis of GdB_<12> by using a Cubic-ambil equipment under the condition of about one hour at 1600℃ at pressure of 5GPa. X-ray analysis clarified that two phases of GdB_6 and GdB_<12> were formed in the ratio of 1:1. Furthermore we tried to do higher pressure synthesis at 10GPa and 1500℃ at last year. Octahedral ambil was included in Cubic-ambil in order to obtain the single phase of GdB_<12>. This method was developed by Prof.Yamanaka. At present the better condition is continuously searched.