Thermoelectric power studies on Nd1.82−xSrxCe0.18CuOy:x≤0.18 superconductors

Abstract

Chemical pressure and electron doping effects in SrPd2Ge2 single crystals J. Appl. Phys. 111, 07E117 (2012) Fluctuation-induced conductivity analyses of Be-doped (Bi0.25Cu0.25Li0.25Tl0.25)Ba2Ca2Cu3O10-δ superconductors in the critical regime and beyond J. Appl. Phys. 111, 033917 (2012) Enhancement of the upper critical field in codoped iron-arsenic high-temperature superconductors J. Appl. Phys. 110, 123906 (2011) Superconductivity at 14.6 K in Fe(SeTe) single crystal and the role of excess Fe J. Appl. Phys. 110, 033914 (2011) Andreev reflection spectroscopy of the new Fe-based superconductor EuAsFeO0.85F0.15: Evidence of strong anisotropy in the order parameter Low Temp. Phys. 37, 280 (2011) Additional information on J. Appl. Phys. In the xϭ0.09 sample, synthesized in the reduced environment, the small magnitude of S is highly metalliclike and its sign is negative, a characteristic of electron conduction. The sign of S for the xϭ0.18 sample shows a crossover below 75 K from negative to positive, in apparent conflict with electronic conduction. Interestingly, after oxygenation this sample exhibits a broadened but positive phonon draglike peak. This oxygenated sample shows overcompensation of the carrier ͑electron͒ concentration. Critical analysis of the data suggests that Sr doping seemingly causes a competition between electron-and holelike conduction. The slope dS/dT is, in general, negative suggesting that the main contribution is coming from the diffusive part. The observed thermopower features seem to fall in line with the theoretical curves of Durczewski and Ausloos ͓Z. Phys. B 85, 59 ͑1991͒; Phys. Rev. B 53, 1762 ͑1996͔͒ based on the inelastic scattering of quasifree electrons by phonons.

Local structure around cations in the Nd(Ce) based superconducting system: an EXAFS study

“…Interestingly, superconductivity in the Ce rich (x = 0.18) T -type NCCO compound has been revived by doping it with alkaline earth elements [7]. The thermoelectric power (TEP) studies on our NCCO x < 0.18 compounds have indicated a negative sign of TEP, suggesting electron conduction [18]. A direct evidence for the local oxygen non-stoichiometry in NCCO SC samples was obtained through a high-resolution analytical SEM technique.…”