Powder synthesis of (Bi, Pb)-1212 superconductors

Abstract

The influence of the stoichiometry of the (Bi,Pb)Sr2(Ca,Y)Cu2Oz on its critical temperature and phase purity was investigated. High yttrium and lead contents raise the 1212 phase content to 95%, whereas the highest critical temperature of 97 K was measured inductively for Bi0.4Pb0.35Sr2Ca0.3Y0.7Cu2.05Oz. The transition from the normally conducting to the superconducting state takes place over a broad temperature regime of at least 40 K. Different 1212 grains within one sample have different cation stoichiometries leading to variable superconducting properties. Furthermore, we show that the ordinary lattice sites of bismuth inside an individual grain are occupied by several different cations, such as Bi, Pb, Cu and Sr and that that of calcium may be occupied by Ca, Y, Sr and Cu. Under optimised processing conditions the stoichiometry Bi0.2Pb0.6Sr1.9Ca0.3Y0.7Cu2.3Oz leads to > 95% phase pure Bi-1212 material. The material is sintered at a temperature 20 °C below the melting temperature of the 1212 compound in air. At this temperature the phase forms within 10 min from the starting oxide and carbonate powders. For longer sintering times the phase decomposes due to Bi and Pb evaporation. When furnace cooled, the 1212 phase remains stable.

Epitaxial growth and superconducting anisotropy ofPbSr2Y1−xCaKomori1, Inaba2, Kaneko3 et al. 2014Phys. Rev. B4120View full textAdd to dashboardCite

“…2(b). For y > 0.20, the films include Bi2212 as a sec- x = 0.29 (1) 0.33 (2) 0.37 (3) 0 50 100 150 200 250 300 y = 0.17 (4) 0.12 (5) 0.00 (3) 0.48 (Bi2212) 0 50 100 150 200 250 300 y = 0.17 (4) 0.12 (5) 0.00 (3) 0.48 (Bi2212) 0 50 100 150 200 250 300 y = 0.17 (4) 0.12 (5) 0.00 (3) 0.48 (Bi2212) 0 50 100 150 200 250 300 (b) y = 0.17 (4) 0.12 (5) 0.00 (3) 0.48 (Bi2212) ondary phase and exhibit distinctly different properties than the single-phase films. The resistivity decreases with increasing Bi concentration and even without the quenching treatment, a sharp superconducting transition takes place at 80 K. Also, the XRD peaks of the Bi2212 phase become more intense.…”

“…The crystal structure of PbSr 2 CaCu 2 O 7+δ (Pb1212) is very similar to that of TlBa 2 CaCu 2 O 7−δ (Tl1212) and HgBa 2 CaCu 2 O 6+δ (Hg1212), both of which have a critical temperature T c greater than 100 K. Pb1212 is expected to be less anisotropic than Tl1212 and Hg1212 because the ionic radius of the element account for the block layers is the smallest in the series (r Hg ≈ r Tl > r Pb ). Among the Pb1212 compounds, Pb 1−y Bi y Sr 2 Y 1−x Ca x Cu 2 O 7+δ (PbBi1212) [1][2][3][4] and Pb 1−y Cu y Sr 2 Y 1−x Ca x Cu 2 O 7+δ (PbCu1212) [5,6] are of specific importance for industry because they mainly consist of the ubiquitous elements Pb and Ca rather than the more exotic Bi and Y, which are currently used for high-T c superconducting wires. However, for Pb1212, the superconducting properties such as anisotropy and critical current are inadequately understood because of the difficulty of obtaining single-crystal samples of this material.…”

Epitaxial growth and superconducting anisotropy of PbSr$_{2}$Y$_{1-x}$Ca$_{x}$Cu$_{2}$O$_{7+δ}$ thin films

“…The resistivity decreases with increasing Bi concentration and even without the quenching treatment, a sharp superconducting transition takes place at 80 K. Also, the XRD peaks of the Bi2212 phase become more intense. Therefore, we conclude that the superconducting transition observed for y > 0.20 is 0.33 (2) 0.37 0.33 (2) 0.37 0.33 (2) 0.37 0.12 (5) 0.00 (3) 0.48 (Bi2212) 0 50 100 150 200 250 300 (b) y = 0.17 (4) 0.12 (5) 0.00 (3) 0.48 (Bi2212) 0 50 100 150 200 250 300 (b) y = 0.17 (4) 0.12 (5) 0.00 (3) 0.48 (Bi2212) 0 50 100 150 200 250 300 (b) y = 0.17 (4) 0.12 (5) 0.00 (3) 0.48 (Bi2212) FIG. 2: Temperature dependence of resistivity and Hall coefficients for samples with different Ca and Bi concentrations.…”