E.M.M. Ibrahim

Structural, electrical, and thermoelectrical properties of (Bi1 − xSbx)2Se3 alloys prepared by a conventional melting technique

Polycrystalline solid solutions of (Bi1 − xSbx)2Se3 (x = 0, 0.025, 0.050, 0.075, 0.100) were prepared using a facile method based on the conventional melting technique followed by annealing process. X-ray analysis and Raman spectroscopical measurements revealed formation of Bi2Se3 in single phase. The electrical and thermoelectric properties have been studied on the bulk samples in the temperature range 100–420 K. The electrical conductivity measurements show that the activation energy and room-temperature electrical conductivity dependences on the Sb content respectively exhibit minimum and maximum values at x = 0.05. The thermoelectric power exhibited a maximum value near the room temperature suggesting promising materials for room-temperature applications. The highest power factor value was found to be 13.53 μW K−2 cm−1 and recorded for the x = 0.05 compound.

Studies on sintering effect on the transport properties of Pb1−xSmxSe

Pb1?xSmxSe (x=0.03, 0.06 and 0.09) compounds are synthesized by solid-state reaction. The x-ray diffraction technique, scanning electron microscope, electrical and thermoelectric power measurements were used to characterize the prepared samples. The samples are sintered at 488?K and the effect of the sintering time on the transport properties was investigated. The metal?insulator transition occurrence depends on both the Sm content and the sintering time. The energy band gap Eg was calculated for the sintered samples of 0.06 Sm composition in the intrinsic region. The Seebeck coefficient measurements show that all the samples under investigation are n-type semiconductor materials with electron carrier predomination at low temperature and hole conduction contribution at high temperature. The power factor S2? was calculated and gave a good indication of the wide application of the investigated compositions as thermoelectric materials.

Effect of heat treatment on the electrical and thermoelectric properties of Sb doped Bi2Se3

Polycrystalline samples of (Bi0.95Sb0.05)2Se3 were prepared using the conventional melting technique at 1273 K, followed by annealing at different temperatures (423, 473, 523 and 573 K) for different time intervals (4, 8, 12 and 16 h). The samples were crystallized in a single phase of Bi2Se3 and no other phases or impurities were observed. The electrical and thermoelectric properties were studied by measuring the electrical conductivity and Seebeck coefficient as functions of temperature in the range 100–400 K. The results exhibited a metal–n-type semiconductor transition for all samples. The power factor (Pf) was calculated to determine the effect of the annealing treatment on the performance of the prepared material as a thermoelectric power generator. The highest room temperature value of the Pf was 6.9 μWK−2cm−1 and was recorded for the sample annealed at 573 K for 16 h. The results confirm the feasibility of using the annealing process to improve the performance of thermoelectric materials.

The thermoelectric properties of Bi-2223 superconductors sintered at different conditions

Structural examinations and thermoelectric power measurements were carried out on Bi1.75Pb0.35Sr2Ca2Cu3O10 samples sintered at different conditions. The thermoelectric power of all samples was found to be positive, and it increases almost linearly with the decrease of temperature up to ~140 K, before falling to zero at Tco. However, the thermoelectric power changes slightly with increasing sintering temperature and time. The normal state results are analyzed in terms of a two-band model with an additional term that is linear in T. The effects of sintering temperature and time on the parameters related to this model have been investigated.