Gh. Cao et al., SYNTHESIS AND CHARACTERIZATION OF NEW CUPRATES WITH A (BI, IN)O MONOLAYER - (BI, IN)SR2(GD, CA)CU2OY, Physica. C, Superconductivity, 221(3-4), 1994, pp. 278-282
New cuprates of (Bi, In)Sr2Gd1-xCaxCu2Oy have been synthesized by the
solid state reaction method in an oxidizing atmosphere. Powder X-ray d
iffraction (XRD) indicates that the samples have space group of P4/mmm
with cell parameters of a=0.38378(5) nm, c= 1.1761(2) nm when x = 0.
The compounds have the same crystal structure as Tl-1212 except for co
ntaining a (Bi, In)O monolayer rather than a TlO layer. Ca2+ substitut
ion for Gd3+ (x less-than-or-equal-to 0.4) results in a decrease of th
e a-axis, which suggests that holes are induced in the CuO2 sheet. A s
emiconductor-to-superconductor transition occurs around x=0.3. The sam
ple of x=0.4 exhibits superconductivity with a T(c)(onset)= 42 K and T
(c)(zero) = 18 K from the measurement of the temperature dependence of
resistivity.