Synthesis of Hg-Re-Ba-Ca-Cu-O superconductors by a two-step method

Author

Wolters, C. ; Amm, K.M. ; Knoll, D.C. ; Peterson, S.C. ; Schwartz, J.

Author_Institution

Nat. High Magnetic Field Lab., Florida State Univ., Tallahassee, FL, USA

Volume

7

Issue

2

fYear

1997

fDate

6/1/1997 12:00:00 AM

Firstpage

1977

Lastpage

1980

Abstract

A new two-step method has been developed to synthesize (Hg,Re)Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ with lower annealing temperatures as compared to conventional methods using a precursor which contains the (Hg,Re)Ba/sub 2/CaCu/sub 2/O/sub y/ phase. In the first step, high phase purity (Hg,Re)Ba/sub 2/CaCu/sub 2/O/sub y/ superconductors are prepared from commercially available Ba/sub 2/CaCu/sub 2/O/sub y/ precursors, HgO, and Re/sub 2/O/sub 7/. In the second step, the finely ground (Hg,Re)Ba/sub 2/CaCu/sub 2/O/sub y/ is mixed with Ca-Cu-O and HgO. This precursor mix is encapsulated in evacuated quartz tubes and annealed for 8 to 48 h between 750/spl deg/C and 850/spl deg/C. The resulting samples have (Hg,Re)Ba/sub 2/Ca/sub 2/Cu/sub 3/O/sub y/ as a majority phase and exhibit a critical temperature of 133 K as prepared. The superconducting grains are platelike and randomly oriented. The grain sizes depend on the annealing time and temperature and reaches up to 30 /spl mu/m diameter and 5 /spl mu/m thickness. Second phases are mainly unreacted Ba/sub 2/CaCu/sub 2/O/sub y/ and Ca-Hg-O.

Keywords

annealing; barium compounds; calcium compounds; grain size; high-temperature superconductors; mercury compounds; powder technology; rhenium compounds; superconducting transition temperature; 133 K; 750 to 850 degC; 8 to 48 hr; Ba/sub 2/CaCu/sub 2/O/sub y/ precursors; HTSC; Hg-Re-Ba-Ca-Cu-O; Hg-Re-Ba-Ca-Cu-O superconductors; annealing temperatures; critical temperature; grain sizes; precursor mix; superconducting grains; synthesis; two-step method; Annealing; Conducting materials; Encapsulation; High temperature superconductors; Laboratories; Land surface temperature; Magnetic fields; Mercury (metals); Superconducting materials; Superconductivity;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.620975

Filename

620975