The effect of chemical substitution on superconductivity in the YBa2Cu3O7

Felner, I.

doi:10.1016/0040-6031(91)80152-9

Cited by 18 publications

(6 citation statements)

References 125 publications

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“…To consider the effect of such substitutions, it is always necessary to keep in mind that raising the level of nonisovalent doping affects the state of the oxygen subsystem by changing the oxygen content and distribution of the oxygen atoms over the unit cell positions. As a result, the oxygen content increases or decreases with growing doping level, depending on the relation between the valencies of substituting and substituted elements [1]. Thus, in analysing data obtained for such systems, account should be taken of the following two effects: (i) influence of an impurity itself, (ii) influence of the impurity-induced change in oxygen stoichiometry.…”

Section: Introductionmentioning

confidence: 99%

Thermoelectric power and band spectrum transformation in Y_1-xCa_xBa_2-xLa_xCu₃O_y

Gasumyants¹,

Elizarova²,

Patrina

2000

Supercond. Sci. Technol.

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The superconducting and normal-state transport properties (resistivity ρ and thermoelectric power S) of two sets of ceramic samples with composition Y 1−x Ca x Ba 2−x La x Cu 3 O y (x = 0−0.4) have been investigated. The co-doping effect was studied at different conditions of the oxygen subsystem, namely, at a near-stoichiometric oxygen content and at that decreased by annealing in vacuum atmosphere. The thermoelectric power changes only slightly with increasing doping level, while the S(T ) dependence acquires additional features, exhibiting a linear increase with decreasing temperature for heavily-doped samples and a rise in the S(T ) curve slope as x grows. The results obtained are analysed in terms of a phenomenological narrow-band model that makes it possible to determine the band spectrum parameters in the normal state and to trace their changes with varying composition. In co-doped Y 1−x Ca x Ba 2−x La x Cu 3 O y , impurities with valencies different from those of the native cations cancel out the influence of one another on the charge balance in the lattice. All the results obtained indicate that the normal-state and superconducting properties of the investigated system are mainly determined by this compensation effect. Comparison of the variation of the critical temperature T c with the changing conduction bandwidth W D shows that there is a correlation between these parameters, according to which the superconducting properties of doped YBa 2 Cu 3 O y depend strongly on the parameters of the band spectrum structure in the normal state. Analysis of how the conduction band is modified and S(T ) transforms suggests that calcium is responsible for additional states in the conduction band.

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Section: Introductionmentioning

confidence: 99%

Thermoelectric power and band spectrum transformation in Y_1-xCa_xBa_2-xLa_xCu₃O_y

Gasumyants¹,

Elizarova²,

Patrina

2000

Supercond. Sci. Technol.

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“…For example, the average allowable A-cation size in the gallate of 1.19 Å is smaller than that for Y(Ca/Sr/Ba) 2 Cu 3 O 7 systems, which is closer to 1.30 Å. 2,3 The difference is likely structural in nature, originating in the blocking layer owing to the different coordination requirements of Ga 3+ and Cu 2+,3+ .…”

Section: Discussionmentioning

confidence: 93%

“…Strontium substitutes for barium in YBa 2-x Sr x Cu 3 O 7-δ only partially up to x ) 1 under ambient pressure, but fully up to x ) 2 under 7 GPa of pressure. 2,3 The solubility of calcium on the barium site is limited even more, reaching only x ) 0.25 at ambient pressure. T c decreases linearly with both Sr 2+ and Ca 2+ substitution.…”

Section: Introductionmentioning

confidence: 99%

“…T c decreases linearly with both Sr 2+ and Ca 2+ substitution. [2][3][4] A novel family of layered cuprates was developed by Vaughey et al 5 and Roth et al 6 by replacing the blocking-layer copper of YBCO with tetrahedrally coordinated Ga 3+ . All the strontium analogues, LnSr 2 Cu 2 GaO 7 (Ln ) La-Nd, Sm-Yb, and Y), can be synthesized at ambient pressure.…”

Section: Introductionmentioning

confidence: 99%

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Cation Disorder in Ga1212

Greenwood¹,

Ko²,

Griend³

et al. 2000

Inorg. Chem.

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Substitution of calcium for strontium in LnSr2-xCaxCu2GaO7 (Ln = La, Pr, Nd, Gd, Ho, Er, Tm, and Yb) materials at ambient pressure and 975 degrees C results in complete substitution of calcium for strontium in the lanthanum and praseodymium systems and partial substitution in the other lanthanide systems. The calcium saturation level depends on the size of the Ln cation, and in all cases, a decrease in the lattice parameters with calcium concentration was observed until a common, lower bound, average A-cation size is reached. Site occupancies from X-ray and neutron diffraction experiments for LnSr2-xCaxCu2GaO7 (x = 0 and x = 2) confirm that the A-cations distribute between the two blocking-layer sites and the active-layer site based on size. A quantitative link between cation distribution and relative site-specific cation enthalpy for calcium, strontium, and lanthanum within the gallate structure is derived. The cation distribution in other similar materials can potentially be modeled.

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“…It is widely accepted that (i) the Y-123-type compounds of tetragonal symmetry are non-superconducting (NSC) and (ii) the superconductivity of the Y-123-type compounds of orthorhombic symmetry is suppressed by Al atoms which substitute for Cu in the basal plane and hence break the chains of the Cu-O squares. These statements have been justified by numerous experimental studies (see, e.g., [1][2][3][4][5][6][7][8][9][10][11]). However, a careful analysis has shown that the relationship between the structure and physical properties of the Al-doped Y(RE)-123-type compounds is more complicated and influenced by several factors.…”

Section: Introductionmentioning

confidence: 99%

Structural features and superconductivity of Al-doped Y(RE)-123-type single crystals

Bocelli¹,

Righi²,

Leonyuk³

et al. 1999

Supercond. Sci. Technol.

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The structure of a series of highly Al-doped superconducting Y(RE)-123 (RE = rare earth element) single crystals was investigated by XRD and NMR methods. On the basis of the data obtained by the structural investigations combined with the studies of magnetic and optical properties, the formation of various superstructures in the samples of pseudo-tetragonal symmetry has been discussed. The correlation between the carrier concentration and T c-values has been determined. The superconductivity (at 70 K) was indicated even at the 2/3 and 1/3 Al substitution for Cu in the basal and CuO 2 planes, respectively, in the phase presumably of a perovskite-like structural type.

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The effect of chemical substitution on superconductivity in the YBa2Cu3O7

Cited by 18 publications

References 125 publications

Thermoelectric power and band spectrum transformation in Y_1-xCa_xBa_2-xLa_xCu₃O_y

Thermoelectric power and band spectrum transformation in Y_1-xCa_xBa_2-xLa_xCu₃O_y

Cation Disorder in Ga1212

Structural features and superconductivity of Al-doped Y(RE)-123-type single crystals

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The effect of chemical substitution on superconductivity in the YBa2Cu3O7

Cited by 18 publications

References 125 publications

Thermoelectric power and band spectrum transformation in Y1-xCaxBa2-xLaxCu3Oy

Thermoelectric power and band spectrum transformation in Y1-xCaxBa2-xLaxCu3Oy

Cation Disorder in Ga1212

Structural features and superconductivity of Al-doped Y(RE)-123-type single crystals

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Product

Resources

About

Thermoelectric power and band spectrum transformation in Y_1-xCa_xBa_2-xLa_xCu₃O_y

Thermoelectric power and band spectrum transformation in Y_1-xCa_xBa_2-xLa_xCu₃O_y