THE EFFECT OF CA DOPING ON THE STRUCTURES OF YBA2CU4O8 AND Y2BA4CU7O14+X SINGLE-CRYSTALS

被引：19

作者：

SCHWER, H ^{[1
]}

KALDIS, E ^{[1
]}

KARPINSKI, J ^{[1
]}

ROSSEL, C ^{[1
]}

机构：

[1] IBM CORP,DIV RES,ZURICH RES LAB,CH-8803 RUSCHLIKON,SWITZERLAND

来源：

JOURNAL OF SOLID STATE CHEMISTRY | 1994年 / 111卷 / 01期

关键词：

D O I：

10.1006/jssc.1994.1203

中图分类号：

O61 [无机化学];

学科分类号：

070301 ; 081704 ;

摘要：

The transition temperature of YBa2Cu4O8 (124) is increased by about 10 K by doping with calcium, whereas Ca substitution in Y2Ba4Cu7O14+x (247) has no effect on T(c). X-ray structure refinements of 13 YBa2Cu4O8 and 12 Y2Ba4Cu7O14+x Ca-doped and undoped single crystals have been performed in order to determine structural changes due to Ca doping. In 124 a major fraction of Ca replaces Y; in 247 Ba1 (single-chain 123 unit) and Y are substituted by Ca in the ratio 3:2. The changes of the charge distribution caused by the substitution of trivalent Y3+ by divalent Ca2+ and ion size effects lead to structural changes in Ca-doped crystals. One structural consequence of the replacement of the small Y (r = 1.02 angstrom) by the larger Ca (r = 1.12 angstrom) is the increase of the distance between the adjacent oxygen planes in the c direction. In 247 the 123 unit is compressed due to the substitution of Bal by the smaller Ca. Ca doping diminishes the buckling of the CuO2 superconducting layers. The Ba-O sublattices in the double-chain 124 units of 247 and 124 are identical and change in the same way upon Ca doping; differences are observed in the Ba-Y sublattice. (C) 1994 Academic Press, Inc.

引用

页码：96 / 103

页数：8

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