Yoshiya Akagi

Synthesis of Superconducting 2212 Phase in the Bi–Pb–Sr–La–Cu–O System

There have been no report about synthesis of the Bi-2212 compound in the Bi–r–La–Cu–O system. We have succeeded in synthesizing the Bi-2212 compound by partial substitution of Pb for Sr and/or Bi in the Bi–Sr–La–Cu–O system. Two samples of nearly the single 2212 phase have been obtained at a nominal composition of Bi1.5Pb0.5Sr2.5La0.5Cu2Oz. Both of the samples crystallize in a psedotetragonal lattice, and their lattice parameters are a = 0.5476 nm and c = 3.085 nm or a = 0.5479 nm and c = 3.055 nm. They are both superconductors. The sample with longer lattice parameter c shows an onset of the resistivity drop and zero resistivity at higher temperatures of about 40 K and about 13 K, respectively. This sample also shows a diamagnetic signal starting at about 35 K with lowering temperature.

Synthesis of new Ru-based cuprate with 1232 structure, RuSr2+xSmCe2−xCu2Oz

Abstract New phase of the Ru-based cuprate with 1232 structure has been synthesized in the RuSr 2+ x SmCe 2− x Cu 2 O z system. The powder X-ray diffraction analysis shows that nearly the single phase can be formed in the x composition range from 0.0 to 0.2. The new phase has a tetragonal unit cell with the lattice parameters of about a =0.384 nm and c =1.70 nm. A bulk sample with x =0.2 shows two anomalies in resistivity at about 12 and 40 K. The former anomaly is considered to originate from the Ru-1232 phase. In temperature dependence of magnetization, the sample shows a diamagnetic signal at about 20 K and ferromagnetic order at about 80 K.

New Ru-Based Layered Cuprates with 1232 Structure in the RuSr2(LnCe2−xSr x )Cu2O z (Ln = Sm, Eu, and Gd) System

New Ru-based layered cuprates with 1232 structure have been synthesized in the RuSr2(LnCe2−xSrx)Cu2Oz (Ln = Sm, Eu, and Gd) system. Nearly single-phase samples are obtained in the composition range from x = 0.0 to 0.2 for Ln = Sm and Eu, and at the composition of x = 0.2 for Ln = Gd. Each of the samples of Ln = Sm, Eu, and Gd with x = 0.2 crystallizes in a tetragonal lattice and lattice parameters a and c are 0.3845 and 1.700 nm, 0.3842 and 1.699 nm, and then 0.3839 and 1.698 nm, respectively. Each of them shows some anomalies at a low temperature in addition to a semiconductor-like temperature dependence of the resistivity. Especially, the sample with Ln = Gd shows two resistivity dropping phenomena at about 16 and 22 K. Then, all of nearly single-phase samples show diamagnetic signals originating from superconductivity, and also rapid increase of magnetization due to a transition from paramagnetic state to ferromagnetic one below 80 K.