MgO在Mg-hBN体系中对合成cBN晶体的影响

 以金属镁粉为触媒，以六角氮化硼为原料，其中加入适量比例的氧化镁，在国产六面顶压机上，在约5.0 GPa压力、1 500～1 800 K温度条件下，合成出了颜色均匀、晶形完整的黄色立方氮化硼单晶体。实验结果表明，在Mg-hBN体系中，氧化镁对合成cBN晶体的颜色及合成温度有很大的影响。     

Studies on the superconductivity for the “111” type iron arsenide superconductor

The “111” type Li _x FeAs (x ranges from 0.8 to 1.2) with Cu₂Sb type tetragonal structure was synthesized with T _c 18 K. The isostructure NaFeAs was further studied, which shows superconductivity with T _c up to 26 K. The effect of pressure on superconductivity was investigated.     

Superconductivity in Topological Semimetal θ-TaN at High Pressure

Recently,θ-TaN was proposed to be a topological semimetal with a new type of triply degenerate nodal points.Here,we report studies of pressure dependence of transport,Raman spectroscopy and synchrotron x-ray diffraction on θ-TaN up to 61 GPa.We find that θ-TaN becomes superconductive above 24.6 GPa with T_c at 3.1 K.The θ-TaN is of n-type carrier nature with carrier density about 1.1 × 10~(20)/cm~3 at 1.2 GPa and 20 K, while the carrier density increases with the pressure and saturates at about 40 GPa in the measured range.However,there is no crystal structure transition with pressure up to 39 GPa,suggesting the topological nature of the pressure induced superconductivity.     

Physical properties and phase diagram of NaFe1-xVxAs

We grew a series of NaFe_1-xV_x As(0 ≤ x ≤ 0.03) single crystals and performed the measurements of resistance,magnetic susceptibility, and specific heat to study the superconducting phase diagram by doping V into Na Fe As. Both the structural and the spin-density-wave(SDW) transitions are slightly suppressed by V-doping. While superconducting transition temperature is enhanced to the maximum value of 15 K when the optimal doping level x = 0.007 and then is suppressed rapidly with further V-doping, displaying a small superconducting dome. Our results suggest that V-impurities should act as strong magnetic scattering centers which cause the sharp suppression of superconductivity in NaFe_1-xV_x As.     

“111”铁基超导体系的发现及压力效应研究

2008年发现的铁基超导体引发了全球超导研究的热潮。在本研究小组发现的铁基“111”体系的基础上,重点介绍“111”体系铁基超导体的压力效应,包括:“111”体系的3个组元LiFeAs、LiFeP、NaFeAs的超导转变随压力的演化;运用压力调控,获得“111”体系的最高超导转变温度;结合同步辐射技术,发现压力调控的“111”型铁基超导体的等结构演化以及对超导起关键作用的As-Fe-As键长和键角与超导转变温度的关联。     

In-Situ Measurement of Electrical Character of PbTe at High Pressure and High Temperature

There is a widespread interest in lead telluride (PbTe) as a good thermoelectric material. We report the temperature dependence of thermopower S(T) and resistance R(T) for PbTe at the different pressures of from 1.8GPa to 5 GPa obtained by using the cubic anvil high pressure apparatus. With increasing pressure, R(T) and S(T) decrease. The effect of pressure on R(T) is larger than that on S(T). The power factor that is determined by thermopower and resistivity increases with increasing pressure. This method is an efficient tool for synthesizing good thermoelectric materials at high pressure and high temperature.     

二元富氢高温超导的实验研究进展

近室温富氢超导材料相关实验报道引发了科研人员对富氢超导的广泛关注,理论预测与实验探索新的富氢超导体及其物性研究已经成为目前超导领域的研究热点。本文结合课题组在富氢超导材料方面的实验研究工作,详细介绍了二元富氢超导体的实验研究进展。     

在Mg-hBN体系中水对cBN晶体合成的影响

 研究了4.5~5.5 GPa、1 400~1 800 ℃ 条件下,两种形态水——自由水与束缚水对在Mg-hBN体系中合成cBN晶体的影响。结果表明：水的形态与添加水的量对合成cBN晶体的颜色、成核率及生长条件有重要影响。自由水可抑制cBN晶体的成核数量,而束缚水可以改变cBN晶体的颜色并降低合成温度。     

“111”型铁基超导材料研究进展

“111”型铁基超导体系包含LiFeAs,NaFeAs和LiFeP三个组员.这三个组员的晶体结构简单,具有非极性解离面等特点,在铁基超导物理机理研究中发挥着独特的作用.本文简要介绍“111”型铁基超导体的研究进展.     

Synthesis,structure, and properties of Ba9Co3Se(15) with one-dimensional spin chains

A new compound with one-dimensional spin chains, Ba9Co3Se(15), was synthesized under high pressure and high temperature conditions and systematically characterized via structural, transport and magnetic measurements. Ba9Co3Se(15) crystallizes in a hexagonal structure with the space group P-6c2(No. 188) and lattice constants of a = b = 9.6765 ? and c = 18.9562 ?. The structure consists of trimeric face-sharing octahedral CoSe6 chains, which are arranged in a triangular lattice in the ab-plane and separated by Ba atoms. The distance of the nearest neighbor of CoSe6 chains is very large, given by the lattice constant a = 9.6765 ?. The Weiss temperature Tθ associated with the intra-chain coupling strength is about -346 K. However, no long-range magnetic order but a spin glass transition at ~ 3 K has been observed. Our results indicate that the spin glass behavior in Ba9Co3Se(15) mainly arises from the magnetic frustration due to the geometrically frustrated triangular lattice.