Phase evolution studies of (TI,Pb)(Sr1.6Ba0.4Ca2Cu3Oy superconductors

Paranthaman, M.; Heatherly, D. E.; Martin, Patrick

doi:10.1016/0025-5408(95)00115-8

Cited by 1 publication

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“…For the Sr-containing end member, it was reported that substitutions of Ba for Sr in the perovskite layer created pinning centers and thus improved the superconducting properties [21–23]. Subsequently, various processing investigations [24] and phase evolution studies of the (Tl,Pb)(Sr,Ba)Ca 2 Cu 3 O y phases [22,25] were conducted. A melt-assisted processing method was found by Doi et al [22] to be an efficient way to introduce pinning centers into Tl-based superconductors.…”

Section: Introductionmentioning

confidence: 99%

Melting and vaporization of the 1223 phase in the system (Tl-Pb-Ba-Sr-Ca-Cu-O)

Cook

Wong‐Ng

Paranthaman

1996

J. Res. Natl. Inst. Stand. Technol.

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The melting and vaporization of the 1223 [(Tl,Pb):(Ba,Sr):Ca:Cu] oxide phase in the system (Tl-Pb-Ba-Sr-Ca-Cu-O) have been investigated using a combination of dynamic methods (differential thermal analysis, thermogravimetry, effusion) and post-quenching characterization techniques (powder x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectrometry). Vaporization rates, thermal events, and melt compositions were followed as a function of thallia loss from a 1223 stoichiometry. Melting and vaporization equilibria of the 1223 phase are complex, with as many as seven phases participating simultaneously. At a total pressure of 0.1 MPa the 1223 phase was found to melt completely at (980 ± 5) °C in oxygen, at a thallia partial pressure (pTl2O) of (4.6 ± 0.5) kPa, where the quoted uncertainties are standard uncertainties, i.e., 1 estimated standard deviation. The melting reaction involves five other solids and a liquid, nominally as follows: 1223→1212+(Ca,Sr)2CuO3+(Sr,Ca)CuO2+BaPbO3+(Ca,Sr)O+LiquidStoichiometries of the participating phases have been determined from microchemical analysis, and substantial elemental substitution on the 1212 and 1223 crystallographic sites is indicated. The 1223 phase occurs in equilibrium with liquids from its melting point down to at least 935 °C. The composition of the lowest melting liquid detected for the bulk compositions of this study has been measured using microchemical analysis. Applications to the processing of superconducting wires and tapes are discussed.

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