Establishment of strongly overdoped states in the HgBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+{delta}} superconductor

Journal Article · Mon Dec 01 04:00:00 EST 1997 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.56.14790· OSTI ID:550552

Fujinami, K ^[1]; Ito, T; Suematsu, H ^[2]; Matsuura, K ^[3]; Karppinen, M ^[2]; Yamauchi, H ^[1]

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1. Materials and Structures Laboratory, and Department of Innovative and Engineered Materials, Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Yokohama 226 (Japan)
2. Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama 226 (Japan)
3. Hokkaido Electric Power Co., Ebetsu, Hokkaido 067 (Japan)

Strongly overdoped HgBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8+{delta}} (Hg-1223) samples with superconducting transitions as low as 97 K were successfully obtained by using HgO, Ca{sub 2}CuO{sub 3}, CuO, and mixtures of highly oxidized BaCuO{sub 2+{epsilon}} ({epsilon}{approx}0.13) and/or BaO{sub 2} powders as starting materials for the high-pressure synthesis at 5 GPa and 950{degree}C. The overdoped state was confirmed by observing negative values for the Seebeck coefficient throughout the temperature range from T{sub c} to 320 K in a thermoelectric power measurement. Also, both of the cell parameters a and c were found to decrease with decreasing T{sub c}, reflecting, respectively, an increase in hole concentration in the CuO{sub 2} planes and the incorporation of oxygen into the HgO{sub {delta}} layer. The oxygen excess {delta} as determined by the Cu(+I)/Cu(+II) coulometric titration method, was {approximately}0.19 in the overdoped sample with T{sub c}=107K. Subsequent reducing annealing in an Ar atmosphere at 280{degree}C increased the T{sub c} to 131 K. Consistently, only positive Seebeck coefficient values were observed up to 320 K for the Ar-annealed sample. A clearly underdoped material with T{sub c}=118K was obtained by annealing the same sample in Ar at a higher temperature ({approximately}400{degree}C). Finally, high-pressure synthesis starting from less-oxidized BaCuO{sub 2+{epsilon}} ({epsilon}{approx}0.06) yielded a Hg-1223 material with {delta}{approx}0.10 and T{sub c}=132K. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 550552
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 22 Vol. 56; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANNEALING
BARIUM OXIDES
CALCIUM OXIDES
COPPER OXIDES
CRYSTAL DOPING
ELECTRONIC STRUCTURE
HIGH-TC SUPERCONDUCTORS
HOLES
MERCURY OXIDES
SEEBECK EFFECT
TRANSITION TEMPERATURE