I. E. Kostyleva

Crystal structure of Ru(Sr, Gd)2(Gd, Sr)Cu2O8 and Ru(Sr, Eu)2(Eu, Ce)2Cu2O10 phases

Abstract We have investigated the synthesis, crystal structure, resistivity and magnetic measurements of phases in the Ru(Sr,Gd) 2 (Gd,Sr)Cu 2 O 8− δ (Ru-1212) and Ru(Sr,Eu) 2 (Eu,Ce) 2 Cu 2 O 10− δ (Ru-1222) systems. Rietveld refinement of the structure was carried out. The refined compositions before and after oxygen treatment are Ru 1.00(1) (Sr 1− y Gd y ) 2 (Gd 1− z Sr z )Cu 2 O 8 ( y =0.03(1), z =0.19(1)) (Ru-1212; T c 1− x Cu x )(Sr 1− y Gd y ) 2 (Gd 1− z Sr z )Cu 2 O 8 ( x =0.05(1), y =0.02(1), z =0.16(1)) (Ru,Cu-1212; T c 1− x Cu x )(Sr 1− y Eu y ) 2 (Eu 1− z Ce z )Cu 2 O 10 ( x =0.04(2), y =0.09(2), z =0.44(3)) (Ru,Cu-1222; T c 1− x Ce x )(Sr 1− y Eu y ) 2 (Eu 1− z Ce z ) 2 Cu 2 O 10 ( x =0.08(2), y =0.15(2), z =0.25(3)) (Ru,Ce-1222; T c(onset) =40 K, T c(zero) =12 K). Ruthenium atoms in these structures are octahedrally coordinated as the (Ru 5+ O 6 ) 7− species. The formal charge of Cu (FC Cu) calculated from the electroneutrality condition of refined phase composition increases after oxygen treatment and achieves an optimal value (FC Cu∼2.14) for the superconducting (Ru,Ce)-1222 phase ( t =1000°C, p =1 GPa, τ =72 h).

Synthesis, crystal structure and properties of superconducting and non-superconducting RuSr2(Nd,Ce)2Cu2O10 phases»

Abstract In this paper we report on the structural, electrical and magnetic properties of a systematic work performed on the synthesis of RuSr 2 (Nd,Ce) 2 Cu 2 O 10− δ (Ru-1222) samples that differ for the number of annealings or sintering temperature in oxygen. This is done in order to highlight the different behaviours of properties as a consequence of the treatments. In particular, we deal with the development or loss of superconductivity after oxygen treatment. Further we discuss the influence of phase composition on superconductivity and magnetic ordering.

Synthesis, structure, superconducting and magnetic properties of (Ru5+1-xMo6+x)(Sr, Gd)2(Gd0.7Ce4+0.3)2Cu2O10-δ (x = 0.0, 0.25, 0.50, 0.75, 1.0)

Abstract We report results of the structural, electrical and magnetic studies in synthesized (Ru1−xMox)Sr2(Gd0.7Ce0.3)2Cu2O10−δ (x=0.0, 0.25, 0.50, 0.75, 1.0) system. The RuSr2(Gd0.7Ce0.3)2Cu2O10−δ phase (x=0) may be both non-superconducting and superconducting with the transition temperature Tc(onset)=32 or 46 K depending on annealing conditions. Annealing under high oxygen pressure shifts Tc to higher temperatures that is caused by change of cation composition. In the (Ru1−xMox)Sr2(Gd0.7Ce0.3)2Cu2O10−δ system, lattice parameters of the different phases corresponding to the different composition decrease with increasing of Mo ions content. This is explained by tetrahedral coordination of Mo ions. The substitution of Mo for Ru suppresses the superconductivity: the phases with x=0.25 and 0.50 are superconductors with Tc(onset)=25 and 22 K, respectively, the phases with x=0.75 and 1.0 show a semiconductive behavior. A magnetic ordering is observed near by ∼95 K for all phases.

Ruthenium-Based Perovskitelike Phases: Synthesis, Structure, and Properties

This paper reports on synthesis and X-ray diffraction study of two groups of phases obtained from batch mixtures: (La,Srk+1(Ru,Cu)kO3k+1 and (La,Sr)3(Ru,Cu)3O6+δ (group I); RuSr2LnCu2O8−δ (Ln = Nd for the first time, Sm, Eu, Gd, (Gd,Y) for the first time), RuSr2(Ln,Ce4+)2Cu2O10−δ (Ln = Pr and Nd for the first time, Sm, Eu, Gd, (Gd,Y) for the first time), and (Ru,Cu)Sr2(Ln,Ce4+)2Cu2O10−δ (Ln = Tb and Y for the first time) (group II). In group I, phases with K2NiF4, Sr3Ti2O7, and cubic perovskite type structures are typically formed; in group II, these are respectively (Ru,Cu)(Sr,Ln)2(Ln,Sr)Cu2O8−δ (1212 type), (Ru,Cu)(Sr,Ln)2(Ln,Ce4+)2Cu2O10−δ (1222 type), and cubic perovskite type structures (the content of the latter depends on the type of Ln). Variation of the formal charge (f.c.) of Ru (group I) and Cu (group II) was evaluated in relation to the cation composition of the phases (groups I and II) and the content of superstoichiometric oxygen (group II). Phases of 1222 type with Ln = Nd, Sm, Eu, Gd, and (Gd,Y) and phases of 1212 type with Ln = Gd exhibited superconducting properties with Tc max ∼ 40 K.

Neutron diffraction study of RuSr2(Nd,Ce4+)2Cu2O10−δ

The crystal structure of the phase produced from the RuSr2(Nd0.7Ce0.3)2Cu2O10−δ (RuNd-1222) batch was studied by neutron diffraction at 290, 150, 50, 2, and 1.4 K. The composition of the phase was determined more precisely, in particular, the neodymium-to-cerium ratio was found to be close to the batch ratio and the oxygen content was determined. The temperature dependences were determined for the interatomic distances, the tilt and rotation angles of the RuO6 polyhedron, and the CuO(3)Cu and RuO(1)Ru bond angles. As temperature decreases, the rotation angle of the RuO6 polyhedron increases, while the tilt angle decreases. Magnetic susceptibility measurements showed magnetic ordering at Tm = 115 K in this phase. Comparative analysis of the structural parameters and Tm value for the RuNd-1222 phase and the known RuSm-1222 and RuGd-1222 phases was carried out.

Dependence of the Structure and Properties of (M,Cu)Sr2(Ln,Ca)Cu2O8−δ (1212) and (M,Cu)Sr2(Ln,Ce4+)2Cu2O10−δ (1222) Phases on the Cation M

The composition and structure of (M,Cu)(Sr,Ln)2(Ln,Ca,Sr)Cu2O8−δ phases, where M = B, Al, Cr, Pb, Bi, Ru, or Mo (1212 type), and (M,Cu)(Sr,Ln(2(Ln,Ce4+)2Cu2O10−δ phases, where M = V, Cr, Mn, Ru, or Mo (1222 type), have been determined. The role of the M cation in the formation of the crystal structures and the superconductivity phenomenon was analyzed. The relationship between the type of M cation and structural parameters was discovered.

Crystal Structure of (Cr,Cu)(Sr,La)2(La,A)Cu2O8-δ (1212-type) and (Cr,Cu)Sr2(Y,Ce)2Cu2O10-δ (1222-type) Phases

Conditions of the synthesis, crystal structures, mechanical properties, electrical resistivities and magnetizations of cuprates with the general formula (Cr,Cu)(Sr,La) 2 (La,A)Cu 2 O 8-δ where A=Ca or Sr of 1212-type and (Cr,Cu)Sr 2 (Y,Ce) 2 Cu 2 O 10-δ of 1222-type were investigated. The compositions of the cuprates and an amount of the impurity phases in the samples were determined. Rietveld refinement of the structure was carried out. It was found that the formal charges of Cu (FC Cu ) calculated from the electroneutrality of refined phase compositions do not achieve value optimal for the appearence of superconducting phases.