Thermoelectric power and thermal conduction studies on the Gd substituted BPSCCO (2234) superconductors


Ozkurt B., Ekicibil A. , Aksan M. A. , Ozcelik B. , Yakinci M. E. , Kiymac K.

JOURNAL OF LOW TEMPERATURE PHYSICS, cilt.147, ss.31-48, 2007 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 147
  • Basım Tarihi: 2007
  • Doi Numarası: 10.1007/s10909-006-9296-3
  • Dergi Adı: JOURNAL OF LOW TEMPERATURE PHYSICS
  • Sayfa Sayıları: ss.31-48

Özet

Measurements of the electrical resistance (R-T), thermoelectric power (S-T) and thermal conductivity (kappa-T) have been carried out on the superconductor Bi1.7Pb0.3-x Gd (x) Sr2Ca3Cu4O12+y , (0.01 <= x <= 0.1). According to the XRD patterns the volume fraction of the Bi-2223 phase decreases in favor of Bi-2212. All the samples show normal metallic behavior down to their relevant transition temperature, T (c) . T (c) -values decrease significantly with increasing Gd concentration in the system. The hole concentration per Cu has been calculated by using the Presland method and found to decrease with increasing Gd content. The thermoelectric power values of the samples are positive and increase in magnitude with increasing the substitution level. The results obtained have been analyzed in terms of "Two band model with linear T-term" and "Xin' s two band model". A very good agreement between the first model and our thermoelectric power data was obtained, but the fit to the second model was poor. The substitution has considerable effect on the thermal conductivity, kappa. The magnitude of kappa is suppressed and a peak appears just below their T (c) , values but becomes weaker and broader when the Gd concentration is increased.