Spectral features of laser induced plasma from YBa2Cu3O7 and GdBa2Cu3O7 highT c superconductors

Laser induced plasma emission spectra from highT _c superconducting samples of YBa₂Cu₃O₇ and GdBa₂Cu₃O₇ obtained with 1.06μm radiation from a Q switched Nd:YAG laser beam has been analysed. The results clearly show the presence of diatomic oxides in addition to ionized species of the constituent metals in the plasma thus produced.     

用Josephson结电子模拟器测量磁通量子2e/h

介绍用Josephson结电子模拟器在政党温度下，模拟测量磁通量子2e/h，用模拟器来研究Josephosn结的特性。该实验可作为普通物理实验中课题设计实验的一个内容。     

High temperature superconducting thin films for microwave filters

YBa₂Cu₃O_7-δ and Tl₂Ba₂CaCu₂O₈ thin films for microwave filters were synthesized by pulsed laser deposition and the two-step thalliation process. Substrate quality requirements and the relation of thin film morphology, microstructure with microwave surface resistance were discussed.     

用电泳技术制备YBCO高温超导厚膜

介绍了电泳技术制备YBCO高温超导厚膜的实验方法和YBCO高温超导厚膜的电学性质测量 ,讨论了在学生小型科研实验或设计实验中开展此实验的学时安排、注意事项和实验内容的扩展 .     

Mass spectrometric study of thermal stability of copper(II) bis(dipivaloylmethanate) vapour

The processes of thermal destruction of copper(II) bis(dipivaloylmethanate) (Cu(dpm)₂) in the temperature range 150°–550°C were studied by using a two-temperature variant of a double chamber Knudsen cell, with mass spectrometric recording of the gas-phase composition. The temperature range of stability of the vapour of the complex in vacuum was determined, as were those of its mixtures with oxygen in different proportions. The temperature dependence of the rate constant of the thermolysis of (Cu(dpm)₂) vapour was obtained. The thermal stability of Hdpm vapour and the influence of oxygen on the thermolysis of the ligand were studied.

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Zusammenfassung Unter Verwendung einer Zweitemperaturenvariante der Knudsenschen Doppelkammerzelle wurde mittels MS-Untersuchung der Gasphasenzusammensetzung im Temperaturbereich 150°–550°C der thermische Abbau von Kupfer(II)-bis(dipivaloylmethanat) (Cu(dpm)₂) untersucht. Es wurde der Temperaturbereich für die Stabilität der gasförmigen Komplexe in Vakuum sowie in Gemischen mit Sauerstoff in verschiedenen Verhältnissen bestimmt. Dabei wurde die Temperaturabhängigkeit der Geschwindigkeitskonstante für die Thermolyse von Cu(dpm)₂ ermittelt. Weiterhin wurde die thermische Stabilität von Hdpm-Dampf sowie der Einfluß von Sauerstoff auf die Thermolyse der Liganden bestimmt.

     

An investigation into the self-propagating high temperature synthesis (SHS) of superconducting ceramics by thermal methods

The SHS route is based on the well-known thermite reaction, in which a strongly exothermic reaction can sustain itself and propagate in the form of a combustion wave until the reactants have been completely consumed. The successful application of the method to the synthesis of superconducting ceramics of stoichiometry RBa₂Cu₃O_y (R=Y, Er, Yb) is reported. The 123 phase was obtained when pellets of R₂O₃, BaO₂ and Cu metal in the correct proportions were dropped into a heater held at 800°C in an oxygen atmosphere and left there for only 10 minutes. Thermal methods (DSC and DTA) are excellent techniques with which to investigate the dependence of the reaction on heating rate, atmosphere and starting composition.     

Bi系高温超导带材冷压工艺优化试验

采用套管法（ＰＥＴ）制备Ｂｉ系高温超导带材,进行了冷压工艺的优化研究。试验结果表明,Ｂｉ系带材所能承受的压力有一个限值,若超过这个限值后,密度虽可提高,但晶粒破碎严重Ｊｃ值反而降低,带材优化的冷压工艺参数是８３８℃／６０ｈ＋冷压＋８３８℃／６０ｈ。第１次压力为２ＧＰａ,第２次２．５ＧＰａ;冷压压下速率为１．５×１０＾－４ｍｍ／ｓ。同时研究还表明冷压的主要作用是提高带材的致密度和晶粒取向度,最终改善     

Time and temperature-based study for the production of high T C phase by sol-gel technique in Pb-bscco system

The high T_C superconducting phase Bi₂Sr₂Ca₂Cu₃Ox (2223) in the Pb-BSCCO system has been produced by EDTA-gel processing using nitrate solutions. The precursor has heated in two stages, at 300 and 800°C each for 2 h, to avoid the burning of the important species involved in the final product. The effects of time (6 to 48 h) and temperature (845 and 855°C) on the formation of the 2223 phase have been studied by sintering the samples in air. Thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and a vibrating sample magnetometer (VSM) have been employed to investigate the powder produced at different stages of decomposition, oxidation and formation of sintered materials from the powders. The volume-fraction of the 2223 phase at 845°C increases with time, the maximum value of the 2223 phase was obtained at 120 h. It has been observed that the formation of the high T_C phase is remarkably enhanced at the temperature of the endothermic peak of the DTA curve. The best result has been obtained in the sample sintered for 24 h at the temperature 855°C (endothermic peak). This also indicated that at 855°C, the large volume-fraction of 2223 phase with T_C 113 K grew in short time and as the sintering time increased, it decomposed into the Bi₂Sr₂CaCu₂Ox (2212) phase and other phases.     

无损耗电阻器的设计方法

利用超导线圈的纯电感器可以模拟成无损耗电阻器，这种新型器件在性能上与电阻器相似，但不产生功率损耗。本文提出了一种用双线性变换法设计无损耗电阻器的方法，并对无损耗电阻器的实现与控制进行了论述。