Crystal structure of (Pb1−xMx)Sr2(Y1−yCay)Cu2Oz and its physical properties

mcA ELSEVIER

Physica C 341 348 (2000) 6 2 9 - 6 3 0 www,elsevier.nl/locate/physc

Crystal structure o f (Pbl.xMx)Sr2(Yl.yCay)CU20 z and its physical properties Y. Ichimaru, K.Sato, S. Kambe, E. Sato, K. Yamaguchi and O. Ishii Graduate School of Science and Engineering, Yamagata Univ, 4-3-16, Jonah, Yonezawa, 992-8510, Japan For exploring novel Pb-contained 1212 compounds, we examined the condition for preparing the (Pb2/3Mv3)1212 phase and the kind of elements substituted for the Pb site. It was revealed that when the M element is divalent or trivaient, single phase (Pb~Mv3)-1212 was formed, indicating that charge balance is an important factor for forming the (Pb2:3M1/3)-1212 phase. Moreover, quenching treatment was proven to be indispensable for forming a single phase of the (Pb2/3M~/3)-1212compound (M = Ag, Cu, Fe, Ga, In, and Ni ). We also investigated the physical properties of (Pbr3Agv3)-1212 phase and confirmed its non-superconductivity.

1. Introduction

2. Experimental

Pb-contained oxide superconductors are classified into the Pb-3212 phase[l] discovered in 1988 and the 1212 phase[2] done in 1989. While the block layer of the Pb-3212 phase is composed of a PbO-Cu-PbO layer, that of the Pb-1212 phase is composed of a Pb(M)O layer. It is well-known that (Pbl.xM)Sr2(Y~.yCa)Cu20 (M = Bi, Cu, V, Cd, Mg, Sr and Ca) compounds show superconductivity whose Tc ranges from 40K to 108K[3]. In this experiment, substitution ofAg, Cu, In, V, Co, Ni, Fe, Ga, AI, Cr, Pb, Mn, Sn, Ti, Ge, Ze, Ce, Nb, Ta and W for Pb was examined for clarifying the conditions &the ionic radius and the valence of the substitutedion M to form single-phase (Pb~3M~)Sr2YCu20 z.

Ceramic samples were prepared by a solid-state reaction. PbO, SrCO3, Y203, CuO and MO x (oxide M) powders were mixed in the nominal composition of (Pb~3M1/3)Sr2YCu2Oz[4]. The powder mixture was calcined at 800 °C for 10h in air, powdered and pressed. The samples were sintered at 1000 °C for 10h, and cooled by quenching (10 minutes). Slow cooling after sintering made impurity phases together with the (Pb2/3M1/3)Sr2YCu2Ozphase. The samples were powdered again before measuring by powder X-ray diffraction (XRD). Impurity-phases were identified by the XRD experiment. We calculated, the ratio, r, of the maximum peak height &the impurity to that of the 1212-phase. The 0 _ 10% samples are identified as single-, impurity-contained- and multi-phases, respectively.

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Y lehimaru et al./Physica C 341 348 (2000) 629-630

3. Results and Discussion

1.3

3.1 (Pb~MI~)Sr2YCu20 '

From the XRD measurement, the structure of the

1.2

samples with M = Ag, Cu, Fe, Ga, In, Ni and Pb were

1.1

found to be similar to those of PbSr2YCu20 z. In contrast, M = Ti, Co and Zr substitution resulted in the impurity-containing-phase. It was also revealed that V, Cr, Mn, Sn, G-e,Ce, Nb,

~1.0

Ta, W or AI was not favored for substitution in this system. In Fig. 1, a phase diagram of

0.7

(Pb2/3M,3)Sr2YCu20 z is shown. It was found that monovalent, divalent and trivalent valences are necessary for forming the (Pb,M)- 1212 single-phase. Ag, Cu, In, Fe, Ga, Ni and Pb were substituted for M of

~

Pb,

l e single-phase • i mpuriW-phase

I

,u t -phase

0.9

~ 0.8

all

llNb

0.6 0.5

I

1

AIIII Gel[I 2 3 4 Val~c¢ of M I

Vl 5

mEW ,

6

Fig. 1 Phase diagram of (Pb~Mv3)Sr2YCu20 z.

(Pb~3M~)Sr2YCu:O z. The range of the ionic radius of M for forming (Pb~3Mvs)Sr2YCu20z is MI+: 0.67 [A] M 2+ :0.57-0.69 [A] M 3+ :0.62-1.19 [A].

stituted for the Pb site. Ag, Cu, In, Fe, Ga, Ni and Pb could be substituted for M of (Pb~3M~)Sr2YCu20 z. We thank J. O. Willis of STC, LANL for useful dis-

3.2 (Pb~Agl/3)Sr2YCu20 '

cussion.

Among the (Pb2:3Mv3)-1212 single-phase samples, when M = Ag the smallest resistance was observed.

References

So we also measured the magnetic susceptibility at low temperature of this sample.

[1]R. J. Cava, B. Batlogg, J. J. Krajewski, L. W.Rupp,

Although a slight decrease in the magnetic susceptibility was found for this sample, a clear drop was not observed, with the result that (Pb~3Ag~/3)-1212 phase is not superconducting.

Marsh, W. F. Peck, Jr., P. K. Gallagher, S. H.

L. F. Schneemeyer, T. Siegdst, R. B. van Dover, P. Glarum, J. H. Marshall, R. C. Farrow, J. V. Waszczak, R. Hull and P. Trevor: Nature 336 (1988) 211. [2]M. A. Subramanian e~. al., Physica C, 157 (1989) 124.J.Y. Lee ~. al., J. Mater. Res., 4 (1989) 763.

4. Conclusion

[3]T. P. Beales, Journal of Materials Chemistry, 1

For exploring novel Pb-contained 1212 compounds, we examined the condition for preparing the (Pb2/3M~a)-1212 phase and the kind of elements sub-

[4]Y. Ichimaru, S. Kamhe, K. Yamaguchi, O. Ishii, Advance in Superconductivity XI (Springer-Verlag Tokyo, 1999) 419-422.

(1998) 1-12.