Synthesis and Properties of New Layr Structured Superconductors

在先前的研究中，我们通过锂嵌入的氮化物层的电子掺杂，从层状结构的β-ZrNC 1衍生出一种新型的超导体。这一发现表明，氮化物层可能成为类似于氧化铜超导体中的CuO_2层的良好的超导基体。在本研究中，我们制备了一系列的β-ZrNCl型层状氮化物，并研究了电子掺杂后超导电性的可能性。对新型层状结构氮化物超导体的发展也作了研究。本研究的主要结果如下：1.通过在β-HfNCl中嵌入锂，获得了一种新的高温超导体，其Tc高达25.5K。注意到Tc（25.5K）比具有岩盐结构的HfN的Tc高得多。采用高压高温条件制备了MNX（M = Zr，Hf ; X = Cl，Br，I）晶体的所有组合。所有的晶体都表现出超导电性的电子掺杂。相变温度主要由金属氮化物层的种类决定.通过与吡啶的反应制备了具有与β ZrNCl结构不同类型的氮化物层的α-TiNCl插层化合物。该化合物在6 K下具有超导电性，这是第一个通过有机碱作为电子供体嵌入层状半导体而得到的超导体.用激光烧蚀技术在Si（111）衬底上制备了ZrN/Si_3N_4人工超晶格薄膜。电子掺杂到薄膜中目前正在研究中。

In a previous study, we derived a new type of superconductor from the layer structured beta-ZrNC1 by electron doping of the nitride layers through lithium intercalation. This finding suggests that the nitride layers may become good matrices of superconductivity like CuO_2 layers of copper oxide superconductors. In this study, a series of beta-ZrNCl type layered nitrides have been prepared and the possibility of superconductivity has been examined after electron doping. Developments of new layer structured nitride superconductors have also been studied. Some important results of this study are the following :1. A new high Tc superconductor with Tc as high as 25.5 K was obtained by intercalation of lithium in beta-HfNCl. Note that the Tc (25.5 K) is much higher than the Tc of HfN with the rock-salt structure.2. All combinations of MNX ( M = Zr, Hf ; X = C1, Br, I) crystals were prepared by using high pressure and high temperature conditions. All of the crystals showed superconductivity by electron doping. The Tcs were mainly determined by the kinds of metal nitride layers concerned.3. Intercalation compounds of alpha-TiNCI having a different type of nitride layers from that of beta ZrNCl structure were prepared by the reaction with pyridine. The intercalation compounds showed superconductivity with Tc at 6 K.This is the first superconductor derived from a layered semiconductor by intercalation of an organic base as electron donor.4. Artificial superlattice films of ZrN/Si_3N_4 were prepared on Si(111) substrate by a laser abration technique. The electron doping into the films is now under investigation.