Electrical and thermal properties of bulk superconductors Eu 0.95Pr 0.05Ba 2(Cu 1− x M x ) 3O 7− δ (M = Fe, Ni, Zn and Mn (original) (raw)
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Physica C-superconductivity and Its Applications, 2010
Measurements of transition temperature, magneto-resistance, thermal conductivity, thermo-electric power and specific heat have been carried out on co-doped samples of Eu0.95Pr0.05Ba2(Cu1-xMx)3O7-δ (M = Fe, Ni, Zn and Mn) compounds. It is found that all samples exhibit metallic behavior, except the co-doped sample of Fe that shows semiconducting behavior. It is seen that the upper-critical field Hc2 decreases with Pr-doping. However, an increase in Hc2 for dopants like Fe and Mn is observed. Thermal conductivity for the pristine sample of EuBa2Cu3O7-δ (Eu-123) exhibits a pronounced hump below the superconducting transition temperature TC. However, the peak height of the hump decreases with Pr-doping and such a feature is further suppressed in the co-doped samples. The negative sign of the measured thermo-electric power of Eu-123 indicates that the dominant carrier in this sample is electron-like, whereas it turns to hole-like for all of the doped samples. A jump in specific heat CP is detected in the pure sample of Eu-123 at TC, while only a change in slope in CP is seen around the transition temperature in the Pr-doped sample.
2010
Measurements of transition temperature, magneto-resistance, thermal conductivity, thermo-electric power and specific heat have been carried out on co-doped samples of Eu 0.95 Pr 0.05 Ba 2 (Cu 1Àx M x) 3 O 7Àd (M = Fe, Ni, Zn and Mn) compounds. It is found that all samples exhibit metallic behavior, except the co-doped sample of Fe that shows semiconducting behavior. It is seen that the upper-critical field H c2 decreases with Pr-doping. However, an increase in H c2 for dopants like Fe and Mn is observed. Thermal conductivity for the pristine sample of EuBa 2 Cu 3 O 7Àd (Eu-123) exhibits a pronounced hump below the superconducting transition temperature T C. However, the peak height of the hump decreases with Prdoping and such a feature is further suppressed in the co-doped samples. The negative sign of the measured thermo-electric power of Eu-123 indicates that the dominant carrier in this sample is electron-like, whereas it turns to hole-like for all of the doped samples. A jump in specific heat C P is detected in the pure sample of Eu-123 at T C , while only a change in slope in C P is seen around the transition temperature in the Pr-doped sample.
Solid State Communications, 2014
In the present communication, measurements of transition temperature, thermal conductivity, thermoelectric power and specific heat have been carried out on pristine and co-doped samples of Dy 0.95 Pr 0.05 Ba 2 (Cu 0.98 M 0.02) 3 O 7 À δ system [M ¼Fe, Co, Ni and Zn]. The electrical resistivity results show that all the samples exhibit metallic behavior. The thermal conductivity results illustrate that for pristine sample of DyBa 2 Cu 3 O 7 À δ , the expected pronounced hump in thermal conductivity is seen below the transition temperature. The hump is suppressed with 5% Pr-doping and this is further suppressed with co-doping. The thermoelectric power measurements show that the pristine sample exhibits hole-like behavior and this continues for doped as well co-doped samples. Pristine sample shows the expected jump in specific heat and with Pr-doping a slope change is observed near the transition temperature.
Solid State Communications, 2011
In the present paper, we present thermal and electrical transport properties of pristine and co-doped samples of high temperature superconductors Gd0.95Pr0.05Ba2Cu2.94M0.06O7-δ. It is found that all the samples, except the Mn co-doped sample, show metallic behavior in the normal state. It is observed that the upper critical field has a correlation with the substituent site of the co-dopant. Thermal conductivity κ(T) of all the samples, except the one with Zn co-doping, exhibits a hump like structure around their respective transition temperatures. A negative sign of the measured thermo-power (S) in Gd-123 indicates that electron-like carriers dominate the heat transport in the pristine sample; whereas a sign reversal in S, as a consequence of the change of dominant carrier upon doping, is observed. Specific heat (CP) measurements show a jump around the transition temperature (TC) for the pristine sample, however, such a jump in CP is strongly suppressed for the doped samples. Critical magnetic field increases with co-doping. Thermo-power shows a change from electron type to hole type. The jump in specific heat vanishes with co-doping.
Solid State Communications, 2011
In the present paper, we present thermal and electrical transport properties of pristine and co-doped samples of high temperature superconductors Gd 0.95 Pr 0.05 Ba 2 Cu 2.94 M 0.06 O 7−δ . It is found that all the samples, except the Mn co-doped sample, show metallic behavior in the normal state. It is observed that the upper critical field has a correlation with the substituent site of the co-dopant. Thermal conductivity κ(T ) of all the samples, except the one with Zn co-doping, exhibits a hump like structure around their respective transition temperatures. A negative sign of the measured thermo-power (S) in indicates that electron-like carriers dominate the heat transport in the pristine sample; whereas a sign reversal in S, as a consequence of the change of dominant carrier upon doping, is observed. Specific heat (C P ) measurements show a jump around the transition temperature (T C ) for the pristine sample, however, such a jump in C P is strongly suppressed for the doped samples.
In this communication, we present some results on thermo‐electric properties of various high temperature superconductors. We have performed measurements on three rare‐earth based cuprate superconductors. All the superconductors were prepared using solid state reaction method. The XRD studies on the present samples indicate that all the samples are in single phase. We observe that among the rare‐earths studied in the present work, Gd‐123 has the highest value of Z. In fact around 200K, the Z‐ value for GdBa2Cu3O7‐δ (Gd‐123) samples is about two times that of the other rare‐earths like YBa2Cu3O7‐δ and EuBa2Cu3O7‐δ. However with Pr‐doping at the rare‐earth site, we get a different trend viz. the figure of merit for Eu0.95Pr0.05Ba2Cu3O7 (Eu‐Pr5%) and Gd0.95Pr0.05Ba2Cu3O7 (Gd‐Pr5%) samples is less than their respective pristine compounds. On contrary, an almost two‐fold increase is seen in Y0.95Pr0.05Ba2Cu3O7(Y‐Pr5%) sample compared to the pristine sample of this series.
Thermal conductivity and thermo-power of ( and ) bulk superconductors
Solid State Communications, 2010
In this paper, we present temperature dependent electrical conductivity ρ(T), thermal conductivity κ(T) and thermoelectric power S(T) for co-doped superconducting compounds Y 0.95Pr 0.5Ba 2(Cu 1- xM x) 3O 7-δ(M=Fe,Mn,Zn and Ni). The XRD patterns confirm that all the samples are single phased. Pristine Y Ba 2Cu 3O 7-δ depicts a pronounced hump-like structure in κ(T) below its transition temperature. With Pr-doping, a reduction in the peak height of the hump is observed. It is found that the hump structure is further suppressed with transition metal co-doping, and is viewed in terms of the phonon scattering with defect structure, electrons and phonons. S(T) data depicting a sign reversal with co-doping, has been analyzed in the framework of a narrow band model.
STRUCTURAL, ELECTRICAL AND THERMAL ANALYSIS OF Y 1-x Eu x Ba 2 Cu 3 O 7- SUPERCONDUCTORS
(Y,Eu)-Ba-Cu-O samples were prepared by solid state method of heat treatment for obtaining single phase materials. The relationship between Y-Eu substitution and the superconducting properties of Y1-xEuxBa2CuO7-d (0.0? x ?0.9) solid solution have been studied. DC resistance measurements showed that Eu substitution was affected the normalized resistance and Tc values. X-ray diffraction analysis showed that the main phase in the prepared (Y-Eu)–Ba-Cu-O samples was the orthorhombic phase. The samples were tended to form plate type of single crystals with preferential orientation in c-direction. The crystallite size of the prepared samples was calculated from X-ray diffraction patterns using Scherer\\\'s equation and has a value of 21nm for pure YBCO and that of Eu content up to 0.9 samples. Thermal analysis of (Y,Eu)-Ba-Cu-O system were performed by means of TG and DTA. The oxygen content was estimated from TG-analysis and it was found to decrease with increasing Eu-content. DTA showed three-regions which were classified as follows: (1) Exothermic peak as a result of chemically bonded dehydration temperature. (2) Endothermic peak due to tetragonal orthorhombic transformation temperature. (3) Exothermic peak which was related to melting temperature.
Journal of Materials Processing Technology, 2008
Y 1−x Nd x Ba 2 Cu 3 O 7−ı (x = 0.0-1.0) samples were prepared by solid-state reaction method. Xray diffraction analysis and SEM investigation were used for structural characterization of the materials obtained. The Nd substitution into the YBaCuO system leads to decrease in the superconducting transition temperature and the zero resistance temperature. The influence of Nd substitution on thermoelectric properties of materials prepared was investigated. The thermoelectric power values of all the samples were obtained to be positive. It was found that the carrier concentration and Fermi energy level decreased with increasing the Nd concentration. A linear temperature dependence in the thermal conductivity down to the superconducting transition temperature and then a sharp rise just below the superconducting transition temperature was obtained. The thermal conductivity magnitude was suppressed by substitution of Nd which indicates the quasiparticles scattering on the Nd containing defects.