Formation and superconductivity of Pr and Nd-substituted Tl1212 phase Tl 0.85 Cr 0.15 )Sr 2 CaCu 2 O 7 (original) (raw)

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.

Preparation of Tl-2212 Cr-Substituted (Tl2-xCrx)Ba2CaCu2O8-δ Superconductor

Journal of Physics: Conference Series, 2018

We have prepared Tl2-xCrxBa2CaCu2O8-δ (Tl-2212) for x=0.0-0.4 by standard solid state reaction with carbonate precursor and Cr2O3 as a source of Cr. The role of Cr substitute the Tl-sites in Tl-2212 superconductor system has been studied. The dc electrical resistance was determined using four point probe and the phase occurrence was studied by X-ray diffraction method. The transition temperature showed metallic normal state behavior for all samples. It was found that the addition of 0.2% mole Cr enhanced the Tc zero for 3.22%, whereas Tconset was enhanced up to 10.47%. The effectiveness substitution of Tl-sites by Cr was achieved in the series of x < 0.2%. Most of the samples were in 14/mmm space group.

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.

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.

Superconducting and magnetic properties of TlSr2Ca1-xRxCu2O7 [R= Pr, Tb]

Physical Review …, 1995

The magnetic and superconducting properties of the TISr 2 Ca 1-x R x Cu 2 O 7 [R=Pr (x=0.2-1.0) Tb (x=0.6 and 1.0)] system are reported. The observation of superconductivity in TISr 2 Ca 0.4 Pr 0.6 Cu 2 O 7 (T c =74 K) suggests that the Pr ions are in the trivalent state. ...

Characterization of superconducting (Tl,Bi)Sr2CaCu2Oy

Physica C: Superconductivity, 1996

The superconducting phase with mixed TI and Bi, namely (Tlo.55Bio.45)Sr2CaCu20y, was synthesized and characterized. Synthesis conditions were studied, and this phase, (TI,Bi)-1212, was found to form preferentially to (TI,Bi)-1223 when Sr was present with no Ba present. X-ray powder diffraction with Rietveld refinement provided structural data. The phase is tetragonal with a = 3.7988(4) A and c = 12.076(1) A, with space group symmetry P4/mmm, and with a platelet crystal morphology. Magnetic-susceptibility data gave an onset of superconductivity T c at 94.9 + 1.3 K with a T c mid of 86.0 + 1.1 K. Magnetic-hysteresis measurements showed that substantial flux pinning occurs in this phase at high temperatures.

Superconductivity at 124 K in (Tl, Pb)Sr2Ca2Cu3O9

Physica C Superconductivity, 1992

We report the preparation of almost phase pure (T10.sPbo.s)Sr2Ca2Cu3Og, which is characterized by high temperature superconductivity with T¢onset= 130 K, Tcmidpoint= 124 K, Tczero= 122.5 K as measured by electrical resistance, and a diamagnetic onset temperature, Tcm~ of 124 K determined by DC magnetic susceptibility. The new procedure involves synthesizing a material with nominal stoichiometry (Tlo.sPbo.5)Srl.6Ca2.4Cu3Og, which is encapsulated in gold foil and sintered at 950°C for 3 h in oxygen, then sealed in an evacuated quartz tube and finally annealed at 700~ 750°C for 5 ~ l0 days. From the results of X-ray diffraction and energy-dispersive X-ray spectrometry (EDS), we have identified the phase responsible for the superconductivity in the annealed sample to be Tlo.sa(3)Pbo.3s(2)Srt.9t2)Ca2.~ o)Cu309. No superlattice and intergrowth along the a* and c* directions were observed but streaks along the c*-axis were found from microcrystallites of the annealed sample.