Yao Yu-Shu

Stability and doping of infinite-layer compound (Ca1−xSrx) CuO2 at ambient pressure

The stability region of the infinite-layer compound (Ca1−xSrx)CuO2 has been investigated in detail along the composition line CaCuO2-SrCuO2 in the SrO-CaO-CuO system. The samples were prepared at 956‡C in air at ambient pressure. Single phase of the infinite-layer structure compound is found to lie at the intersection of two different phase regions and its stability region is extremely narrow nearx = 0.16. Temperature also has pronounced effect on the stability of the infinite layer structure. A trial of doping into the infinite layer compound (Ca1−xSrx)CuO2 was performed by partial substituting (Ca, Sr) with lanthanum.

120K SUPERCONDUCTING TRANSITION IN HOT-PRESSING BI-PB-SR-CA-CU-O SYSTEM

Abstract Superconducting critical transition with onset at 123K and zero resistance at 101K are obtained by hot pressing in the Bi-Pb-Sr-Ca-Cu-O system. A.C.χ measurements show that there are 85K superconducting phase except for 110K superconducting phase. This sample has been investigated by X-ray powder diffraction and SEM observation, the X-ray powder diffraction patterns of two main superconducting phase can be indexed in the forms of orthorhombic cells with lattice parameters a=5.420 A , b=5.447 A , c=30.845 A and a=5.420 A , b=5.447 A , c=36.884 A respectively. As expecting SEM experiment shows that a lower porosity was obtained in the hot pressed sample.

Superconductivity of (R0.4Pr0.6)0.5Ca0.5Ba2Cu3O7-δ( R= La, Pr, Nd, Sm, Eu, Gd and Y) Prepared Under High Pressure

The nearly single phase (R0.4Pr0.6)(0.5)Ca0.5Ba2Cu3O7-delta compounds (R = La, Pr, Nd, Sm, Eu, Gd and Y) with T-c about 100K were prepared under high pressure and high temperature using the cubic-anvil apparatus. The T-c is much higher than that of the traditional R-123 superconductors without doping Ca on the rare-earth site. For various rare earths with different ionic radii, the (R0.4Pr0.6)(0.5)Ca0.5Ba2Cu3O7-delta compounds have almost the same critical temperature. This is different from the result of the ion-size effect of rare-earth ions in R1-xPrxBa2Cu3O7-delta compounds. Our results show that Pr has the same properties as other rare earths in the 123-phase compounds due to the doping of Ca.

High-resolution electron microscopy studies of high-pressure synthesized mercury-based superconductor

Studies of high-pressure synthesized Hg-Ba-Ca-Cu-O superconductor by electron diffraction and high-resolution electron microscopy are reported. The results of electron diffraction indicate that two superconducting phases 1212 and 1223 exist in the sample and their cell parameters area=b=3.8 Å,c=12.7 Å anda=b=3.8 Å,c=15.8 Å, respectively. High-resolution electron micrographs were taken from the two phases Hg-1212 and Hg-1223 and from the region of the intergrowth of the two phases. The relation between the structure and superconducting transitional temperatureTc is discussed.