Chemical stabilization of Hg-based superconductors

Hahakura, S.; Shimoyama, Jun–ichi; Shiino, O.; Hasegawa, Tetsuya; Kishio, K.

doi:10.1016/0921-4534(94)91682-9

Cited by 26 publications

(30 citation statements)

References 3 publications

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“…If Sr is substituted for some of the Ba cations, T c decreases 11 and the synthesis of single-phase materials necessitates the use of either high pressure 12 or a second substituent with a valence greater than 2 on the Hg site. 13 The lattice parameters of Sr-123 and Sr-Hg12(nϪ1)n decrease with respect to those of unsubstituted materials in a way similar to that observed by applying external pressure. 14 The introduction of Sr induces similar decreases of T c in compounds as different as 123 and Hgbased ones; it would then be interesting to study these structures in detail in order to elucidate the structural mechanisms associated with the decreases of T c .…”

Section: Introductionsupporting

confidence: 52%

Structural and electronic effects of Sr substitution for Ba inY(Ba1−xSrx
Licci
¹
,
Gauzzi
²
,
Marezio
³

et al. 1998
Phys. Rev. B
72
7
37
1
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To unveil the structural mechanisms associated with T c variations induced by either mechanical or chemical pressure, samples of the Y(Ba 1Ϫx Sr x ) 2 Cu 3 O w system with xр0,0. 02,0.1,0.25,0.35,0.5,0.625,0.75,1, as well as those with xϭ0.5 and wϭ6.685,6.80,6.96,6.98, have been prepared and characterized. Characterization includes crystal structural refinements based on powder neutron diffraction data taken at room temperature, electron microscopy for detecting a possible Ba/Sr ordering, and resistive and magnetic measurements of the superconducting transition. The effects of Sr substitution on the structural parameters are equivalent to those of a pressure of approximately 10 GPa/x. The main difference is the thickness of the superconducting block CuO 2 -Y-CuO 2 , which increases with increasing x and decreases with increasing pressure. As a consequence of the displacement of O4 from the ͑0, 1 2 ,0͒ to the (x, 1 2 ,0) position, the Ba/Sr-O4 distance decreases with increasing Sr content. At constant w, T c decreases at the rate of 20 K/x. For xϾ0, the maximum of T c occurs at a value of w higher than for xϭ0. For xϭ0.5 the thickness of the superconducting block increases with increasing w and consequently with increasing T c . This indicates that, at least in this system, the thickness of the superconducting block is not the key parameter controlling T c . The stress of the Ba/Sr and the Y sites, estimated from the bond valence sums ͑BVSs͒, decreases with increasing x. For xϭ0.5, the BVS values are almost equal to the formal values of 2ϩ and 3ϩ, respectively. The average BVS of Cu1 and Cu2 increases with increasing x. However, this does not correspond to a real increase because the total charge of the Cu cations, as determined by iodometric titration or neutron diffraction, remains constant with x. Our analysis of the structural data suggests that the relaxation of the Ba/Sr layer hinders the charge transfer from Cu1 to Cu2, which accounts for the decrease of T c with increasing x. ͓S0163-1829͑98͒05645-8͔

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Section: Introductionsupporting

confidence: 52%

Structural and electronic effects of Sr substitution for Ba inY(Ba1−xSrx
Licci
¹
,
Gauzzi
²
,
Marezio
³

et al. 1998
Phys. Rev. B
72
7
37
1
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“…Few months later, the 1212, 1223 and 1234 members were stabilized, corresponding to the general formula HgBa2Cam_iCumO2m+2+a with m = 1, 2, 3 In the strontium based cuprates, Hgl_~MxSr2Cam_lCumOZm+2+a ((Hg,M)SC), mixed layers have been conceived with M = Cu, Sr, Bi, Tl, Pb, Pr, Cr, Mo, Ce, Re; they are either of 1201-type [14][15][16][17] or of 1212-type [18][19][20][21][22][23][24]. In the barium based cuprates, Hgi-~M~Ba2Ca~-iCu~02~+2+( (Hg,M)BC), M can be Ca, Bi, Pb, V, Mo, W, Ti, Cr, Al, Ga, Ge [25][26][27][28][29][30] Figure Ib, the 1223 cuprate Hgo,BBio,2Ba2CaZCu30g+s, where the positions of the cations are imaged as white dots so that the sequence of the layers along c can be easily identified (marked in the right part of the micrograph).…”

Section: Introductionmentioning

confidence: 99%

Mixed Layers in Copper Based Superconducting Materials

Hervieu

Tendeloo

Michel

et al. 1996

Microsc. Microanal. Microstruct.

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Abstract. 2014 Recently discovered series of high Tc superconductors, characterized by the existence of two types of cations within the same layer, are presented. The first family concerns the mercury based cuprates, Hg1-xMxA2Cam-1CumO2m+2+03B4, with A = Ba and/or Sr, which exhibit structures closely related to that of the thallium cuprates TlBa2Cam-1CumO2m+3. They differ from the thallium cuprates by a high oxygen deficiency at the level of the mercury layer. It is shown that cations such as M = Cu, Pb, Tl, Bi, Ce, Pr, Cr, V, Mo, W, Ti, Sr, Ca,... can partially substitute for mercury ions, stabilizing the structures. The cationic composition of the layer depends indeed on the nature of the M cation but also on that of the alkaline earth A. For given A and M cations, the x value remains unchanged even when the number of copper layers varies. M and Hg cations are either statistically distributed over the same site or ordered. Different types of ordering have been detected. Another way of generating mixed layers is to shear periodically the structure, leading to the formation of the so called "collapsed phase". In the collapsed bismuth cuprates, bismuth and copper segments, a few octahedra long, alternate in strongly waving layers. In the collapsed oxycarbonates, carbonate groups and M cations are ordered within the intermediate layer so that they can be simply described from a partial and ordered substitution of carbon for Hg,Tl, Bi and other M cations building the intermediate layer. The oxycarbonitrates (Y1-xCax)nBa2nCu3n-1(C,N)O3O7n-3 can also be described as an ordered substitution of carbon for copper in the 123 matrix. The different families of superconducting materials which are generated by such mechanisms are described as well as the way the different species are distributed within the mixed layers. Their influence on the physical properties are discussed.

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“…A typical XRD pattern (figure 1a) of (Hg,Re)-1201 sample shows that the main peaks are due to tetragonal 1201-type structure [1]. A few additional peaks due to minor impurity phases, viz., SrCuO 2 and Sr 2 CuO 3 , were also identified [1,3,4].…”

Section: Resultsmentioning

confidence: 99%

“…Since only a few reports are available on (Hg,Re)-1201, further investigations on this system are desirable. Hahakura et al [1], however, have observed that the stabilization of superconducting (Hg,Re)-1201 phase requires a lower content (x) of Re vis-à-vis Cr or Mo [1]. Therefore, in this work, we report on the synthesis, characterization and superconducting properties of nominal composition (Hg 1−x Re x )Sr 2 CuO 4+δ (x = 0.10 and 0.20).…”

Section: Introductionmentioning

confidence: 90%

See 1 more Smart Citation

Magnetization study of mercurocuprate (Hg,Re)Sr2CuO4+δ

et al. 2002

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The nominal (Hg 1−x Re x )Sr 2 CuO 4+δ (x = 0.10 and 0.20) samples were synthesized at ∼ 920 • C in partial vacuum. The compound with x =0.10 exhibits superconductivity at ∼ 54 K while the composition x = 0.20 is non-superconducting down to 5 K. On cooling below 10 K in an applied field of 4 kOe, the former causes a noticeable upturn in the field cooled (FC) magnetization signal. Such a change in magnetic response is also reflected in the magnetic hysteresis loop generated at 9 K. We attribute this effect to a paramagnetic contribution arising from Re in (Hg,Re)-1201 phase.

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Chemical stabilization of Hg-based superconductors

Cited by 26 publications

References 3 publications

Structural and electronic effects of Sr substitution for Ba inY(Ba1−xSrx
Licci
¹
,
Gauzzi
²
,
Marezio
³

et al. 1998
Phys. Rev. B
72
7
37
1
View full text Add to dashboard Cite

Structural and electronic effects of Sr substitution for Ba inY(Ba1−xSrx
Licci
¹
,
Gauzzi
²
,
Marezio
³

et al. 1998
Phys. Rev. B
72
7
37
1
View full text Add to dashboard Cite

Mixed Layers in Copper Based Superconducting Materials

Magnetization study of mercurocuprate (Hg,Re)Sr2CuO4+δ

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Chemical stabilization of Hg-based superconductors

Cited by 26 publications

References 3 publications

Structural and electronic effects of Sr substitution for Ba inY(Ba1−xSrxLicci1, Gauzzi2, Marezio3 et al. 1998Phys. Rev. B727371View full textAdd to dashboardCite

Structural and electronic effects of Sr substitution for Ba inY(Ba1−xSrxLicci1, Gauzzi2, Marezio3 et al. 1998Phys. Rev. B727371View full textAdd to dashboardCite

Mixed Layers in Copper Based Superconducting Materials

Magnetization study of mercurocuprate (Hg,Re)Sr2CuO4+δ

Contact Info

Product

Resources

About

Structural and electronic effects of Sr substitution for Ba inY(Ba1−xSrx
Licci
¹
,
Gauzzi
²
,
Marezio
³

et al. 1998
Phys. Rev. B
72
7
37
1
View full text Add to dashboard Cite

Structural and electronic effects of Sr substitution for Ba inY(Ba1−xSrx
Licci
¹
,
Gauzzi
²
,
Marezio
³

et al. 1998
Phys. Rev. B
72
7
37
1
View full text Add to dashboard Cite