Crystal Growth of Bi 2 Sr 2 CaCu 2 O x Superconductor by Zone Melting Technique

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Crystal Growth of Bi2Sr2CaCu2Ox Superconductor by Zone Melting Technique T. Iwamoto 1*, S. Watauchi 1,2 and I. Tanaka 1,2 1

Institute of Inorganic Synthesis, Yamanashi University,

Miyamae 7, Kofu 400-8511, Japan 2

CREST Project, Japan Science and Technology Corporation, Japan

ABSTRACT We attempted to grow single crystals of Bi2Sr2CaCu2Ox (Bi-2212) by Traveling Solvent Zone Melting (TSZM) technique using a gold crucible to stabilize the molten zone as well as to control the composition of Bi-2212 single crystals. As the results of crystal growth, chemical composition of the grown crystals was determined to be Bi: Sr: Ca: Cu = 1.97(4): 1.75(7): 0.88(3): 2.0, which was close to that of feeds. TSZM growth may be effective on the control of composition of Bi-2212 crystals. Superconducting properties of the grown crystal of Bi-2212 were Tc,onset=85 K and ∆Tc=10 K. INTRODUCTION Large and high quality single crystals of Bi2Sr2CaCu2Ox (Bi-2212) are desired for application in superconducting electronic devices and for the basic physical understanding of high-Tc superconductors.

Various growth techniques such as a traveling solvent floating zone

(TSFZ) method [1, 2], top seeded solution growth (TSSG) method [3], self-flux method [4-8] and Vertical Bridgman (VB) method [9, 10] were proposed for the crystal growth of Bi-2212. Slow-cooling processes such as TSSG, self-flux and VB methods cause precipitation of secondary phases and compositional fluctuation, since Bi-2212 is a solid solution as well as an incongruent-melting compound in ternary oxides system. In TSFZ growth, it is very difficult to maintain a stable molten zone during crystal growth because the shape of the grown crystal becomes plate-like due to the highly anisotropic growth rate.

The unstable molten zone easily

introduces the appearance of the defect structure such as an impurity phase.

Therefore, a new

growth technique to grow single crystals of Bi-2212 is still now desired to improve the quality, the homogeneity and the crystal size of Bi-2212 single crystals. II9.5.1

We have developed a new growth technique, the traveling solvent zone melting (TSZM) method using a gold crucible to obtain the high quality single crystals of Bi-2212.

This

technique is a growth technique combined with the TSFZ method and the VB method to transfer the molten solvent stably during the crystal growth.

Gold does not contaminate the Bi-2212

crystals grown in the gold crucible [11]. In this study, the growth furnace and the gold crucible were designed and prepared, and then single crystals of Bi-2212 were grown by the TSZM method. EXPERIMENT The powders of Bi2O3, SrCO3, CaCO3, and CuO (>99.99%) were used as raw materials for crystal growth of Bi-2212.

The raw materials were mixed at the atomic ratio of

Bi:Sr:Ca:Cu=2.1:1.8:1.0:2.0 and 2.1:1.5:1.0:1.8 for feed and solvent, respectively.

The mixed

powder was calcined in air at 770 Û&IRUK  )RUSUHSDUDWLRQRIIHHGWKHFDOFLQHGSRZGHUZDV pulverized and put into a rubber tube to form a cylinder shape and then p