Preparation of Tl-2212 Cr-Substituted (Tl2-xCrx)Ba2CaCu2O8-δ Superconductor (original) (raw)
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Superconducting Properties of Te-Substituted (Tl2-xTex) Ba2CaCu2O8-δ
Solid State Phenomena
The Tl2-xTexBa2CaCu2O8-δ (Tl-2212) high temperature superconductors with x = 0.0-0.5 have been prepared by the standard solid-state reaction method. The precursor powder were sintered at 900°C for 24 h with several grindings and heating. The powder were then pressed into pellets and heated at 910°C in oxygen flow for 4 min followed by furnace cooling. The electrical resistance versus temperature dependence measurements showed metallic normal state behavior for all samples. Substitution of Te at the Tl-site led to multi-phasic samples. The x = 0.4 sample showed the highestTc zero= 98 K and Tconset= 111K. The Tl-2212 phase increased from 50% for x=0 up to 92% in the x= 0.4 sample.
Structure and superconducting properties of (Tl 0.8 Bi 0.2)(Sr 1.6 Ba 0.4) Ca 2 Cu 3 O 9− δ
The "1223" structural type of high temperature superconductor, (Tlo.sBio.2XSrl.6Ba0.4)Ca2Cu309 -8(referred to as T1,Bi-1223), based on oxides of thallium and bismuth has been prepared by reaction of prereacted powders of (Srl.6Ba0.4)Ca2Cu307 with T1203 and Bi203. The as-synthesized material has a superconducting transition temperature (T c) of 113 K, which is relatively unaffected by post-annealing either in an oxygen or an argon atmosphere. Polycrystalline samples of T1,Bi-1223 exhibit a high persistent current density (Jp) of 1.62 × 107 A/cm 2 at 5 K and 1 tesla, and maintain significant Jp values to temperatures over 60 K. The structure of TI,Bi-1223 has been refined using neutron powder diffraction data. The crystal structure is quite similar to those of T1-1223 related compounds, P4/mmm symmetry with a = 3.8211 A and c = 15.4235 A. The atomic sites of thallium and oxygen in the rock-salt TIO plane are slightly vacant and occupancies of the sites were determined by the neutron diffraction study. 0921-4534/95/$09.50 © 1995 Elsevier Science B.V. All fights reserved SSDI 0921-4534(95)00453-X
Electrical Properties of Li Substituted (Tl0.85Cr0.15)Sr2-x Li x CaCu2O7 Superconductor
Journal of Physics: Conference Series, 2018
The effects of Li substitution for Sr in (Tl 0.85 Cr 0.15)Sr 2-x Li x CaCu 2 O 7 (Tl-1212) with x = 0-0.10 were investigated. Tl-1212 superconductor pellets were prepared via solid-state reaction and precursor method. The samples were characterized by x-ray diffraction and fourpoint probe methods. The XRD patterns showed that all samples formed mixed phases of Tl-1212 and Ca 0.3 Sr 0.7 CuO 2 (CSCO). The temperature-dependent resistance measurements showed metallic-behavior for all samples with onset transition temperature, T c onset between 96 K and 105 K and zero resistance temperature, T c zero between 85 K and 94 K. The transition-width, ∆T c of all samples was in the range of 4 K to 11 K. The x = 0.02 and 0.07 sample showed increase in T c onset to 105 K and 102 K, respectively. This work showed that Li improved the transition temperature for x = 0.02 and 0.07 samples although the dominant phase was not Tl-1212.
Journal of Materials Science-materials in Electronics, 1999
The derivatives of Tl-1212 type phase superconductors with nominal starting compositions Tl0.85Cr0.15)Sr2(Ca1-xRx)Cu2O7 where R = Pr or Nd (Ca series) together with Tl0.85Cr0.15)Sr2(Ca1-xRx)Cu2O7 (Sr series) for x = 0 - 0.5 have been prepared and investigated by d.c. electrical resistance and powder X-ray diffraction analyses. Partial substitution of Ca with Pr or Nd has the advantage of stabilizing the tetragonal
Composition dependence of the superconducting properties of the Tl-Ba-Ca-Cu-O system
Physica C: Superconductivity, 1992
A series of superconducting samples with nominal composition TI2Ba2Ca._ ~Cu.O2.+4 (1-< n< 11) have been prepared by a two-step method using barium nitrate (instead of barium oxides or barium carbonate). The phase analysis and structural analysis were performed by X-ray diffraction and an electron microprobe. The four-probe resistance and AC susceptibility measurements show that all the samples are superconducting with Tc above 105 K except the n= 1 sample, which has a Tc of 88 K. The highest Tc (To(M)= 124 K) in this series is obtained in the n=5 sample. It is found that there is a correlation between T¢ and lattice parameter a of the 2223 phase. Tc increases when lattice parameter a decreases. Several new phases are found by the microprobe analysis. The reaction route and the stability of the samples are also discussed.
Formation of Tl 0.85Cr 0.15Sr 2CaCu 2O 7− δ superconductor from ultrafine co-precipitated powders
Materials Letters, 2006
The Tl 0.85 Cr 0.15 Sr 2 CaCu 2 O 7−δ superconductor has been successfully synthesized from ultrafine powders prepared via the co-precipitation method from nearly saturated solutions of metal acetates and 2-isopropanol solution of oxalic acid. The metal oxalates powders were calcined at 600°C for 20 h. The calcined powders were pelletized and heated for 3, 4 and 5 min at 980°C. The zero-resistance temperature, T c-zero for samples heated at 3, 4 and 5 min is 88 K, 100 K and 92 K, respectively. XRD results showed the existence of tetragonal structure which belongs to the high-T c 1212 phase. SEM micrographs showed ultrafine grains of about 1 μm or less for samples heated for 3 min. The grain size increases as the heating time is increased. These ultrafine powders can be useful in various applications such as starting material for high temperature superconductor tapes fabrication.
Preparation and X-ray characterization of superconducting and related Tl2Ba2CuO6 phases
Materials Research Bulletin, 1988
Polycrystalline oxides of the form T12Ba2CuO 6 have been synthesized by a solid-state reaction technique. TI2Ba2CuO 6 displays a variety of properties, ranging from superconductivity to semiconductivity depending on the preparation conditions. X-ray diffraction analysis showed that a superconducting T12Ba2CuO 6 phase with Tc~20K has a bodycentered tetragonal structure similar to those of the T12CaIBa2Cu20 ~ and T12Ca2Ba2Cu3Ot0 high Tc superconductors. The tetragonal unit cell dimensions refined from a high quality powder diffraction pattern are a=3.8632(2)~,, c=23.160(1)~,, and V=345.7(2)• 3.
Physica C-superconductivity and Its Applications, 1993
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High-quality T1 2 Ba 2 CuO 6 + X (2201) compounds were synthesized using a high-pressure route. Starting from T1 2 Ba 2 0 5 and CuO, the reactions yielding either the orthorhombic or the tetragonal (superconducting) phases were carried out under 100 bar of oxygen or argon and helium, respectively. Preferential thallium losses are prevented and high sintering temperatures can be used to obtain pure samples with large 2201 grains. The experiments performed include metallographic examinations, X ray diffraction, microprobe analysis, plasma emission spectroscopy, HRTEM, AC susceptibility, Meissner field cooling, hysteresis loops, normal-state susceptibility and specific heat measurements.