New highT c cuprate (Tl1−x Cr x ) (Sr2−y Ba y )Ca2Cu3O9Z. Y. Chen, Z. Z. Sheng, Y. Q. Tang, Y. F. Li, L. M. Wang, and D. O. Pederson Citation: Applied Physics Letters 62, 3034 (1993); doi: 10.1063/1.109130 View online: http://dx.doi.org/10.1063/1.109130 View Table of Contents: http://scitation.aip.org/content/aip/journal/apl/62/23?ver=pdfcov Published by the AIP Publishing Articles you may be interested in Effects of Sr2+ substitution on photoluminescence characteristics of Ba1−x−ySryZrSi3O9:xEu2 +phosphors J. Appl. Phys. 116, 223507 (2014); 10.1063/1.4903531 High-pressure and high temperature synthesis and magnetic characterization of niobio-cuprate Nb 0.9Sr 2 Y Cu 2.1 O 7.9 J. Appl. Phys. 101, 09G110 (2007); 10.1063/1.2711284 New family of high Tc superconductors in the (Tl1−x M x )Sr2(Ca1− y Y y )Cu2O7−δ system (M=IVAand VA elements) Appl. Phys. Lett. 57, 2492 (1990); 10.1063/1.104180 Timeresolved optical emission during laser ablation of Cu, CuO, and highT c superconductors:Bi1.7Sr1.3Ca2Cu3O x and Y1Ba1.7Cu2.7O y J. Appl. Phys. 66, 4435 (1989); 10.1063/1.343939 Bulk superconductivity with T c (zero) up to 95 K in a Tl0.5Pb0.5Ca0.9Ce0.1Sr2Cu2 oxide with anY1Ba2Cu3O y like structure Appl. Phys. Lett. 54, 2464 (1989); 10.1063/1.101536

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New high-T, cuprate (II, -xCr,J (Sr2_,Bay)Ca2Cu309 Z. Y. Chen,a) Z. Z. Sheng, Y. Q. Tang, Y. F. Li, L. M. Wang,b) and D. 0. Pederson Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701

(Received 22 December 1992; accepted for publication 19 March 1993)

A new series of 1223-type (Tl,Cr) -based cuprates, (Tl,Cr) (Sr,Ba) 2Ca2Cu30Z, have been successfully synthesized and identified by powder x-ray diffraction and electron diffraction analyses. Ba partial substitution for Sr promotes the formation of (Tl,Cr)-based 1223-type compounds. Nominal samples, (Tl, -,Cr,) - (Sr, _ $a,) CaaCuxO, , with 0.15 ~~~0.50 and 0.50~<1.50 are pure or nearly pure-1223 phase and exhibit T,(,c=O) in the range of 104-114 K. This new (Tl,Cr)-based high-T, material may be of importance in practical applications.

After the TlBaCaCuO superconducting system was discovered,‘.’ and (TlO ) ,Ba,Ca,- iCu,OZn + 2 with m = 2 and 1 was identified,3*4 the TlSrCaCuO system was found to be also superconducting at 20 and 70 K.’ In fact, there is a series of superconducting compounds in the TlSrCaCuO system: (T10)mSrZCan-iCun02n+2 with m=l and n = 1-3.6 The Sr series compounds are not easy to form. But, by partially substituting Pb for Tl, the 1223 phase (Tl,Pb)Sr,Ca,Cu30, forms easily and T, is as high as 122 K.7 Multi- phase nominal samples (Tl,Bi) Sr,Ca,CusO, were re- ported with T, (onset) of 119 K and T,( p=O) of 106 K,’ which may originate from a (Tl,Bi)- 1223 phase. After that, 1223-type compounds, for example, 120 K (T1,Pb,Bi)Sr&!a,Cu30,,9 115 K (Tli -xBi,) SrZCazCu30,, 10 114 K (Tlo.dbo.5 )Sr,.6B~.4Ca~CU30s.~,11 and 120 K (T10,,Pbo,S)Sr2Ca2Cu309 (Ref. 12) were reported. Re- cently, the Tl-based 1223 compounds received special at- tention because they were found to have a very high critical current density at 77 K compared with Tl-2223 or Bi-2223 superconductors according to the magnetic hysteresis mea- surements. I3 Tl- 1223 superconductors actually have less anisotropy compared with other cuprate superconductors due to stronger interlayer coupling between CuOs planes because of the presence of only a single insulating (TlO) layer in the compound, leading to an enhanced coupling along the c-axis and hence to a three-dimensional charge transfer character, rather than the two-dimensional char- acter of the Tl-2223 compound.i3-” Therefore, Tl-1223 is an excellent compound of choice for fabricating Ag- or (Au,Pd)-sheathed superconducting wires and tapes by the powder-in-tube process.‘“”

Because Cr has the capability to promote the forma- tion of superconducting phases and to increase T, in Cr- substituted 1201-phase TISr,CuOS (Ref. 19) and Cr- substituted 1212-phase T1Sr$aCuzO-I,‘0V21 we carried out a series of experiments to synthesize Cr-substituted 1223- phase TlSr,Ca2Cu30,. The results showed that the (Tl,Cr) - 1223 phase (Tl,Cr) Sr,Ca,Cu~OB is rather difficult

n’Permanent address: Department of Applied Chemistry, University of Science and Technology of China, Hefei, Anhui, 230026, People’s Re- public of China.

“Present address: Department of Geology, University of New Mexico, Albuquerque, NM 87 13 1.

to synthesize, but when Sr is partially substituted by Ba, the 1223 phase forms easily. In this letter we report the preparation of the new 1223-type cuprate (Tl,Cr) ( Sr,Ba),Ca,Cu30, in the pure or nearly pure form and the characterization by x-ray diffraction and electron diffraction. Their T,( p=O) are in the range of 104-l 14 K. This new (Tl,Cr)-based 1223-type high-T, material may be of importance in practical applications.

Samples with nominal compositions (Tl,-,Cr,) (Srz-,,Ba,,)Ca&!u30, (x=0.00, 0.25, 0.50; y=O.l, 0.25, 0.50, 0.75, 1.00, 1.50, 2.00) were prepared using high- purity T&O,, Cr,03, SrO, BaO,, CaO, and CuO powders by a two-step solid-state reaction method. T1203 was ex- cessive by 20% to compensate Tl loss by vaporization. In the typical procedure, precursors ( Srz-$a,,)CazCu30, were prepared first. Appropriate amounts of SrO, BaOz, CaO, and CuO were mixed and ground well in an agate mortar. The mixture powders were preheated at 840 “C for 24 h in an air atmosphere and then cooled to room tem- perature. The products were again ground, and were sub- jected to another heating cycle. This procedure was re- peated two to three tinies to obtain a uniform powder. Then, the resultant precursor powers were mixed with ap- propriate amounts of T&O3 and Cr,O,, ground, and pressed into pellets of about 12 mm in diameter and about 2 mm in thickness with a hydraulic press. The pellets were placed in a covered alumina crucible, introduced into a preheated tube furnace and heated at 900-1000 “C! in Aow- ing oxygen atmosphere for about 5 h. Finally, the temper- ature of the furnace was decreased naturally to room tem- perature.

Powder x-ray diffraction measurements were per- formed with Cuba radiation using a DIANO DTM 1057 diffractometer. The samples were also examined in detail using a JEM 2000FX analytical electron microscopy with a TN-5500 energy-dispersive x-ray spectroscopy (EDXS) analyzer. Resistance was measured by the typical four- probe technique with an ac frequency of 27 Hz. The sam- ple was connected to the leads using silver paste. All mea- surements were carried out in a commercial APD refrigerator with computer control and processing.

We first tried to prepare samples with a 1223 starting composition (Tl, -,C!r,) SrzCaZCu30,. But the samples prepared by the typical procedure do not easily form the 1223 phase. Rather, when x=0.1-0.5, the samples mainly form the 1212 phase and exhibit T, around 100 K, which

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- . -me- .~ . .- - - ~ . -

(4

-I-

6 0 2 0 (degree)

1 0 2 0 3 0 4 0 5 0 6 0 2 0 (degree)

FIG. 1. P o w d e r x- ray dif fract ion pat terns for the nomina l samp les (Tls&r,,,,) (Sr , -$a , )Ca$&O, with y= (a ) 0.10, (b) 0.25, (c) 0.50, (d) 0.75, (e) 1.00, (f) 1.50, a n d (g) 2.00. T h e indexes m a r k e d in (a), (c), (f), a n d (g) a re hk l of 1212, 1223, 1223, a n d 2 2 2 3 phases, respect ively.

is s imi lar to that of samples p r e p a r e d with a 1 2 1 2 start ing composi t ion (Tl, -XCrX)Sr ,CaCu,O, .”

A fter extensive exper iments , w e found that w h e n S r is part ial ly subst i tuted by B a , the samples with a start ing composi t ion (Tl,-,Cr,) (Sr ,Ba)&!a2Cu90, f rom the 1 2 2 3 p h a s e m u c h easier . F igure 1 shows p o w d e r x-ray diffrac- t ion pat terns for a ser ies of samples with nomina l c o m p o - si t ions of (T le75Cr0 ,25) (Sr ,_ , ,BaY)Ca,CulOz with y = O . 10, 0.25, 0.5, 0.75, 1.00, 1.50, a n d 2.00. It can b e s e e n that the

0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0

T E M P E R A T U R E (K)

FIG. 2. Res is tance- temperature curves for the nomina l samp les (Tb. , ,Cro,2s)(Srz_Ba,)Ca?CuJ0, wi th y=O. lO, 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, a n d 2.00.

samp le of y = O . 1 0 is domina ted by the 1 2 1 2 phase. W ith a n increase of the a m o u n t of B a , the 1 2 2 3 p h a s e increases. T h e samp le of y = O .25 b e c a m e domina ted by the 1 2 2 3 phase. W h e n y = O .50, 0.75, a n d 1.00, the samples a re p u r e 1 2 2 3 phase. T h e samp le of y = 1 .50 is still p u r e 1 2 2 3 phase. However , wi th a fur ther increase of the B a a m o u n t, 2 2 2 3 p h a s e appea rs a n d the samp le of B a = 2 .00, i.e., wi thout Sr, b e c a m e domina ted by the 2 2 2 3 phase. Note that the p rep - ara t ion tempera tu re for- the system decreases with the in- c rease of B a , a n d the p repara t ion tempera tu re for samples of y=1 .50 a n d 2 .00 dec reased f rom 1 0 0 0 to 9 7 0 a n d 9 4 0 “C, respect ively.

T o invest igate the effect of Cr o n the format ion of the 1 2 2 3 phase, w e p r e p a r e d ser ia l samples with f ixed Sr /Ba rat io but var iab le Tl/Cr ratio. For nomina l samples (Tl,-,Cr,) (Sr l .zBa0.75)Ca&!usOz with x = = O .O O , 0.25, a n d 0.50, the samples of x=0 .25 a n d 0 .50 a re near ly p u r e 1 2 2 3 phase, whe reas the samp le of x=0 .00 is a mixture of 1 2 2 3 a n d 2 2 2 3 phases. W ith the increase of B a a m o u n t, the 1 2 2 3 p h a s e forms easier . For nomina l samples (Tl, _ ,Cr ,> (Sro .soBal .so)CazCu30z with x=0.00, 0.25, a n d 0.50, al l samp les form a near ly p u r e 1 2 2 3 phase. Obviously , a n appropr ia te rat io of B a /S r a n d a n appropr ia te a m o u n t of Cr a re very impor tant for the format ion of (Tl,Cr ) - 1 2 2 3 or T l -1223 phases. F r o m a n overal l v iew, the opt imal format ion reg ion for s ing le 1 2 2 3 p h a s e (T1,_ ,Cr , ) (Sr l_~ay)Ca2Cu30, is x = = O . l5AX50 a n d y=o.50-1.50.

T h e x-ray dif fract ion pat terns of the samples a re i ndexed by a leas t - roo t -mean-square re f inement p rocedure . A s a n example , Tab le I lists the i ndexed x-ray dif fract ion da ta for the p u r e 1 2 2 3 p h a s e samp le (T10,75Cr0 .25) (SrL, ,Bae,, ) Ca,Cu,O,. T h e uni t cel l p a r a m - eters a re a = 3 .821 h; a n d c = 15 .34 A . This samp le was a lso sub jec ted to e lect ron dif fract ion (ED) study. T h e uni t cel l pa ramete rs de te rm ined f rom E D a re a = 3 .9 A a n d c = 15 .1 A , wh ich is consistent wi th the results f rom the p o w d e r x-ray diffraction. Tab le II summar izes the uni t cel l p a r a m - eters a n d p h a s e t ransformat ion for the ser ies of samples ( T lo, ,5Cro,25) (Sr , -$a, )Ca&!u,O, . It can b e clear ly s e e n that the subst i tut ion of la rger B a for smal ler S r makes bo th a a n d b axes of the uni t cel l expand .

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TABLE I. Indexed powder x-ray diffraction data for Ub.7+h.d (Sr,.2sBao.7s)Ca2Cu,O,.

No. +r Int.

H K L (-4) (%)

1 0 0 1 15.147 15.341 <5 2 0 0 2 7.685 7.670 <5 3 0 0 3 5.118 5.114 <5 4 0 0 4 3.838 3.835 7 5 1 0 2 3.422 3.420 19 6 1 0 3 3.063 3.061 33 7 1 0 4 2.701 2.707 100 8 0 0 6 2.557 2.557 16 9 1 0 5 2.393 2.392 12

10 0 0 7 2.192 2.192 6 11 1 1 5 2.028 2.028 7 12 2 0 0 1.911 1.911 26 13 1 1 6 1.857 1.857 6 14 1 0 8 1.714 1.714 10 15 2 0 5 1.622 1.622 8 16 1 1 8 1.564 1.564 15

The synthesis of pure 1223 phase samples itself implies that Cr has entered in the lattice. Energy-dispersive x-ray spectra (EDXS) clearly show that Cr, together with Tl, Sr, Ba, and Cu, has entered the crystalline lattice. While Cr has definitely entered into the lattice of 1223-phase com- pounds, there is no direct data at this moment to determine the site of Cr in the 1223 phase. According to the result for the Cr-substituted 1212 phase T1Sr2CaCu207,20 a major part of Cr substitutes for Ca while substitution for Tl is minor and there is no evidence for Cr substitution in the Cu site. In view of the fact that Cr goes to the Tl site in the 1201 phase,” we surmise that Cr substitutes for Tl.

The (Tl,Cr) (Sr,Ba) 2Ca,Cu30, samples were subjected to resistance-temperature measurements. Figure 2 shows the resistance-temperature curves for the serial samples ( Tlo,,,Cro,, ) ( Sr, _$a,,) Ca&usO, . The pure 1223 phase samples with y=O.50-1.50 have T, of 105-114 K. The sample of x=0.10 is dominated by the 1212 phase, and the zero-resistance temperature is as high as above 100 K, which is consistent with our previous results for the 1212 phase.” It must be pointed out that the sample of y=2.00 (without Sr), which is dominated by the 2223 phase, has a superconducting transition temperature not as high as that of the pure 1223 phase sample of y=1.50, which

TABLE II. Unit cell parameters of (Tb,,Cro.,,) (Srz-$a,)Ca,Cu,Q, prepared at 1000 “C.

Note

0.10 3.802 12.04" Dominant 1212 phase 0.25 3.815 15.32' Dominant 1223 phase 0.50 3.817 15.31 Nearly 1223 phase pure 0.75 3.821 15.34 Pure 1223 phase 1.00 3.836 15.41 Nearly 1223 phase pure 1.5ob 3.840 15.50 Pure 1223 phase 2.00’ . . . . . Mixture of 2223 and 1223 phases

aCalculatecl from 1212- or 1223-type dominant phases. ‘Prepared at 970 ‘C. ‘Prepared at 940 ‘C.

indicates that an appropriate ratio of Sr/Ba is important not only to the formation of the (Tl,Cr)-based 1223 phase, but also to its superconductivity. For the serial samples (Tl, -,Cr,) ( Srl.,oBao.so)Ca2Cu30, and (Tli-,Cr,) (Sro,soBa,,50)Ca,Cu,0,, the samples of x=0.25 are of optimal superconductivity with T,(p=O) of 108 and 114 K, respectively. All these results indicate that the cooperative effects of Tl and Cr, and Sr and Ba, are very important to the formation of the 1223 phase and to its high-T, superconductivity. In the present experiments, the T, of the 1223 phase is in the range of 104-114 K, which is not as high as the highest T, around 120 K reported for the 1223 phase (see, for example, Refs. 7 and 9), indicating that there is potential to improve T, of the (Tl,Cr)-based 1223 phase. The work along this line is in progress.

This work is supported by the Arkansas Energy Office. The electron microscopy was completed in the Electron Microbeam Analysis Facility of Department of Geology of the University of New Mexico.

‘2. Z. Sheng and A. M. Hermann, Nature 332, 138 (1988). ‘2. Z. Sheng, W. Kiehl, J. Bennett, A. El Ali, D. Marsh, G. D. Mooney, F. Arammash, J. Smith, D. Viar, and A. M. Hermann, Appl. Phys. Lett. 52, 1738 (1988).

‘R. M. Hazen, L. W. Finger, R. J. Angel, C. T. Prewitt, N. L. Noss, C. G. Hadidiacos, P. J. Heaney, D. R. Veblen, Z. 2. Sheng, A. El Ali, and A. M. Hermann, Phys. Rev. Lett. 60, 1657 (1988).

4S. S. P. Parkin, V. Y. Lee, A. I. Nazzal, R. Savoy, R. Beyers, andS. J. LaPlace, Phys. Rev. Lett. 61, 750 (1988).

‘Z. Z. Sheng, A. M. Hermann, D. C. Vier, S. Schultz, S. B. Oseroff, D. J. George, and R. M. Hazen, Phys. Rev. B 36, 7074 (1988).

‘S. Matsuda, S. Takeuchi, A. Soeta, T. Suzuki, K. Aihara, and T. Kamo, Jpn. J. Appl. Phys. 27, 2062 (1988).

7M. A. Subramanian, C. C. Torardi, J. Gopalakrishnan, P. L. Gai, C. Calabrese, T. R. Askew, R. B. Flippen, and A. W. Sleight, Science 242, 249 (1988).

sC. Dong, Z. Z. Sheng, X. Fei, L. Sheng, J. H. Wang, and A. M. Hermann, Physica C 161, 257 (1989).

9T. Wada, T. Kaneko, H. Yamauchi, and S. Tanaka, Proceedings of the 2nd International Symposium on Superconductivity (ISS ‘89), Novem- ber 14-17, 1989, Tsukuba, Ibaraki, Japan (1989); p. 179.

“0. Inoue, S. Ada&i, and S. Kawashima, Jpn. J. Appl. Phys, 29, L763 (1990).

“T. Kamo, T. Doi, A. Soeta, T. Yuasa, N. Inoue, K. Aikara, and S. Matsuda, Appl. Phys. Lett. 59, 3186 (1991).

“R. S. Liu, S. F. Hu, D. A. Jefferson, and P. P. Edwards (unpublished). “R. S. Liu, D. N. Zheng, J. W. Loram, K. A. Mirza, A. M. Cambell, and

P. P. Edwards, Appl. Phys. Lett. 60, 1019 (1992). 14D H Kim K. E. Gray, R. T. Kampwirth, J. C. Smith, D. S. Richeson, . . 7

T. J. Marks, J. H. Kang, J. Talvacchio, and M. Eddy, Physica C 177, 431 (1991).

“T. Sasaoka, A. Nomoto, M. Seido, T. Doi, and T. Kamo, Jpn. J. Appl. Phys. 30, L1868 (1991).

“Z. F. Ren and J. H. Wang, Appl. Phys. Lett. 61, 1715 (1992). 17B. A. Glowacki and S. P. Ashworth, Physica C 200, 140 (1992). “P J Kung M. P. Maley, P. G. Wahlbeck, and D. E. Peterson, J. Mater. . . ,

Res. (to be published). t9Z. Z. Sheng, Y. F. Li, Y. Q. Tang, Z. Y. Chen, and D. 0. Pederson,

Solid State Commun. 83, 205 ( 1992). ‘OZ. Z. Sheng, D. X. Gu, Y. Xin, D. 0. Pederson, L. W. Finger, C. G.

Hadidiacos, and R. M. Hazen, Mod. Phys. Lett. B 5, 635 (1991). “Y. Q. Tang, Z. Z. Sheng, Z. Y. Chen, Y. F. Li, and D. 0. Pederson

Appl. Phys. Lett. 60, 3057 ( 1992). Published without author correctior

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