Ultrasonic study on Bi-based high-Tc superconductors with preferred orientations

Jian Dong; Tingzhang Deng; Fengying Li; Yushu Yao

doi:10.1103/PhysRevB.42.301

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Ultrasonic study on Bi-based high-Tc superconductors with preferred orientations

Jian Dong, Tingzhang Deng, Fengying Li, Yushu Yao

DOI 10.1103/PhysRevB.42.301 · Physical Review B

T1

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Abstract

Ultrasonic experimental studies on Bi-based ceramic superconductors are reported. The specimens used in our experiments were hot pressed after sintering in air; therefore, a preferred orientation of the granules was obtained. The frequencies of ultrasound were about 10 MHz, both for longitudinal and for transverse waves. It has been found that anomalies in the attenuation coefficient and sound velocity occur near 220 K, in the range between 10 and 50 K above Tc, and at Tc, respectively. The investigation shows that the pretransition in the range between 10 and 50 K above Tc leads to a tendency of softness and instability in crystal lattice, and the superconducting transition is present on the background of a rapid decrease in attenuation with the decrease in temperature. It is believed that a strong superconducting fluctuation exists above Tc. The deformation-potential model for acoustic-phonon–electron interaction, which is the basis of BCS theory, may be unsuitable for the high-Tc superconductors. A model of superconductivity due to optical-phonon–electron coupling is suggested.

Source-reported materials — not catalogue approval

Formula	Reported Tc (K)	Pressure (GPa)	Type
BiSrCaCu2Ox Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	86	Pressure not reported	unknown
BiSrCaCu2Ox Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	106	Pressure not reported	unknown
(Bi,Pb)SrCaCu1.6Ox Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	86	Pressure not reported	unknown
(Bi,Pb)SrCaCu1.6Ox Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	9.7	Pressure not reported	unknown
(Bi,Pb)SrCaCu1.6Ox Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	8.9	Pressure not reported	unknown
(Bi,Pb)SrCaCu1.6Ox Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	32	Pressure not reported	unknown
Bi2Sr2CaCu2Ox Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	10.8	Pressure not reported	unknown
Bi2Sr2CaCu2Ox Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	70	Pressure not reported	unknown
Bi2Sr2CaCu2Ox Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula.	86	Pressure not reported	unknown