Effect of Co-Ga Paired Substitution on Superconductivity in YBa2Cu3O7-delta (original) (raw)
Related papers
Effect of Co-Ga paired substitution on superconductivity in YBa2Cu3O7-d
2004
The effect of Co-Ga paired substitution on the superconducting properties of YBa 2 Cu 3 O 7-δ (Y-123) has been investigated by X-ray diffraction, ac susceptibility, dc resistivity and oxygen content measurements. We report in this paper the results of our studies on the paired substitution of a magnetic and non-magnetic ion at Cu site in Y-123, while keeping the total dopant concentration fixed. The simultaneous substitution of Co and Ga at Cu site shows variation in the transition temperature (T c ), oxygen content and hole concentration as a function of change in the balance of magnetic (Co) and nonmagnetic (Ga) concentration. Orthorhombicity (D), given as (b-a)/a, also varies as a function of increasing dopant concentration. The variation in T c due to Co-Ga substitution is discussed in the light of dopant valency and hole filling mechanism. KEYWORDS A. Oxides, A. Magnetic materials D. Superconductivity
EFFECT OF Co–Ga PAIRED SUBSTITUTION ON SUPERCONDUCTIVITY IN YBa 2 Cu 3 O 7-δ
Modern Physics Letters B, 2004
The effect of Co-Ga paired substitution on the superconducting properties of YBa 2 Cu 3 O 7-δ (Y-123) has been investigated by X-ray diffraction, ac susceptibility, dc resistivity and oxygen content measurements. We report in this paper the results of our studies on the paired substitution of a magnetic and non-magnetic ion at Cu site in Y-123, while keeping the total dopant concentration fixed. The simultaneous substitution of Co and Ga at Cu site shows variation in the transition temperature (T c ), oxygen content and hole concentration as a function of change in the balance of magnetic (Co) and nonmagnetic (Ga) concentration. Orthorhombicity (D), given as (b-a)/a, also varies as a function of increasing dopant concentration. The variation in T c due to Co-Ga substitution is discussed in the light of dopant valency and hole filling mechanism. KEYWORDS A. Oxides, A. Magnetic materials D. Superconductivity
Superconducting properties of YBa2Cu3O7−δ with partial rare earth substitution
Physica C: Superconductivity, 1991
Superconducting properties of the YBa2Cu307_~ compound with partial rare earth substitution (20 atomic pct substitution for yttrium) have been studied. Among the 14 rare earth elements investigated, La, Ce and Pr caused suppression in To, while other elements had no effect. Some of the rare earths (Sm, Gd, Eu), when partially substituted for Y, resulted in a slight improvement in intragrain Jc (flux pinning) as measured magnetically. Although the rare earth elements have widely different ionic radii, all the (RE) Ba2Cu3OT_~ phases have been found to be soluble in YBa2Cu3OT_6 with no detectable segregation observed by SEM and energy dispersive X-ray analysis.
Effect of Cd and Cd-Ca Substitution on the Superconductivity in Y1-xPrxBa2Cu3O7-delta Superconductor
Journal of Superconductivity, 1997
The structural and superconducting properties of Y~-x-,PrxCd,-=Ca=Ba2Cu3Ov_;s system are investigated using X-ray diffraction, ac susceptibility, dc resistivity, and oxygen content measurements. The effect of increasing Cd concentration substituting the Y-site in Yo.sPro.2Ba2Cu307-6 suppresses the superconducting transition temperature and lowers the hole concentration, unlike that of Ca substitution in Yo.sPro.2Ba2Cu307-6 which increases T~ due to hole doping by Ca. The suppression of Tc due to Cd substitution can be counterbalanced by simultaneous hole doping by Ca which increases the T,: with increasing Ca concentration. In spite of similarity in the ionic radii and valency, the role played by Cd and Ca substitution at the Y-site in the Yo.sPro.2Ba2Cu307-~ system is opposite in nature as Cd doping helps in Tc suppression due to the Pr effect, suggesting that Cd does not provide the necessary holes like Ca substitution which helps to increase the ~. by the hole doping mechanism.
Journal of Applied Physics, 2005
Results of phase formation, resistivity (ρ), and thermo-electric power (S), are reported on Y 1-x Ca x Ba 2 Cu 2.7 Co 0.3 O 7 compounds with x = 0.1 and 0.2. Pristine compound i.e. without Co or Ca substitution crystallizes in orthorhombic structure with space group P/mmm. Cu-site Co substituted compound i.e. YBa 2 Cu 2.7 Co 0.3 O 7 is tetragonal. With simultaneous doping of Ca at Y site in Co substituted compound i.e. Y 1-x Ca x Ba 2 Cu 2.7 Co 0.3 O 7 the tetragonal nature still remains. ρ(T) measurements showed superconducting transition temperature (T c) to decrease from 90K (YBa 2 Cu 3 O 7) to 33 K for YBa 2 Cu 2.7 Co 0.3 O 7 which with further Ca substitution increases from 33K to 53K (Y 0.9 Ca 0.1 Ba 2 Cu 2.7 Co 0.3 O 7) and 67 K for Y 0.8 Ca 0.2 Ba 2 Cu 2.7 Co 0.3 O 7. T c decreases first with Cu-site Co substitution by hole-filling and later recovers by simultaneous hole creation by Y site Ca substitution. Room temperature thermoelectric power S(300 K), which is an indirect measure of mobile carriers shows the decrease of carriers with Co doping and creation by Ca substitution. Our results demonstrate the hole filling by Co substitution is compensated by simultaneous Ca substitution.
Physica C: Superconductivity, 2005
We report systematic studies of structural, microstructural and transport properties of Y 1-x Ca x Ba 2 Cu 3 O 7-δ bulk samples with 0.20 ≥ x ≥ 0.0. The partial substitution of Ca 2+ at Y 3+ site in YBa 2 Cu 3 O 7-δ leads towards slightly overdoped regime, which along with disorder in CuO 2 planes is responsible for decrease in superconducting transition temperature (T c ) of the doped system. The microstructural variants being studied by transmission electron microscopy (TEM) technique in imaging and selected area diffraction modes revealed an increase in the density of twins with increase in Ca concentration despite the fact that there is slight decrease in the orthorhombicity. This is against the general conviction of decrease in twin density with decreasing orthorhombicity. An increase in twin density results in sharpening of twin boundaries with increasing Ca concentration. These sharpened twin boundaries may work as effective pinning centers. A possible correlation between microstructural features and superconducting properties has been put forward and discussed in the present investigation.
Microstructural and Superconducting Properties of YBa2Cu3-xCoxO7-δ System
Integrated Ferroelectrics, 2011
Bulk superconductor samples of YBa2Cu3-xCoxO7-δ with x = 0, 0.01, 0.03, 0.05 are synthesized by solid-state reaction route. Both x-ray diffraction and electron microscopy have been employed to study the phase identification, intergrowths, dislocations and the local structure of these samples. Transition temperature of the samples has been determined by four probe resistivity measurements. The x-ray diffraction patterns indicate that the gross structure/phase of YBa2Cu3-xCoxO7-δ do not change with the substitution of Co up to x = 0.05. The zero resistance critical transition temperature [Tc(R = 0)] is found to decrease and critical current density (Jc) increases with the increased concentration of cobalt in the compound. The Jc enhancement for the cobalt doped samples may be resulting due to flux pinning from some defects such as planar defects, stacking faults and micro defects (twin, domains etc.) and the rapid suppression in Tc may be due to the cooper pair breaking and the hole filling in the CuO2 planes.
The effect of LiOH addition to the superconducting properties of YBa2Cu3O7-x
Journal of Superconductivity, 1997
The effect of LiOH addition to YBa2Cu3O7-x is presented. The crystal structure remains orthorhombic, but the orthorhombic splitting decreases from 0.0171 at 2 at. % Li to 0.0158 at 50 at. % Li. The critical temperature exhibits a decrease from 91.18 to 83.79 K in the same range of lithium concentrations. From the magnetization curves were obtained the lower critical fields and the intragranular critical current density. The latter exhibits a negative power law, jc ~ B -~, with a .~ 1/2. V-I characteristics are typical for grained superconducting materials: V<(I-L) ~8"~. The transport critical current dependence on temperature and magnetic field is also presented.
Journal of Superconductivity, 1997
The structural and superconducting properties of Y1−v−η PrNCd{η}¨zCaz Ba2Cu3O7−δ system are investigated using X-ray diffraction, ac susceptibility, dc resistivity, and oxygen content measurements. The effect of increasing Cd concentration substituting the Y-site in Y0.8Pr0.2Ba2Cu3O7-δ suppresses the superconducting transition temperature and lowers the hole concentration, unlike that of Ca substitution in Y0.8Pr0.2Ba2Cu3O7-δ which increasesT c due to hole doping by Ca. The suppression ofT c due to Cd substitution can be counterbalanced by simultaneous hole doping by Ca which increases the Tc with increasing Ca concentration. In spite of similarity in the ionic radii and valency, the role played by Cd and Ca substitution at the Y-site in the Y0.8Pr0.2Ba2Cu3O7-δ system is opposite in nature as Cd doping helps in Tc suppression due to the Pr effect, suggesting that Cd does not provide the necessary holes like Ca substitution which helps to increase the Tc by the hole doping mechanism.