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We synthesized the polycrystalline manganite of La5/8Ca3/8MnO3 with three different manganese routes prepared through a solid state reaction method. The effects of the manganese route selection on the structure, electrical transport and magneto-transport properties were examined in this study. The samples were characterized using X-ray diffraction (XRD) and SEM to identify their structure and morphology. XRD analysis confirmed that all samples were in single phase with orthorhombic structure and belonged to the Pnma space group. The average grain sized samples with manganese route of Mn2O3 and MnCO3 had a grain size of 1.2-8.7 μm and 2-7.5 μm, respectively. For the MnO2 route, the sample had a small melt-like shape with higher porosity. The metal-insulator transition temperature, TMI, for LCMO (Mn2O3), LCMO (MnO2) and LCMO (MnCO3) samples were 270 K, 266 K and 258 K, respectively. All the samples showed negative magneto-resistance with significant increase in value near the TMI temperature. The highest CMR (colossal magneto-resistance) ratio was found in LCMO (Mn2O3), -22.06% at 270 K, followed by -16.69% for LCMO (MnO2) at 80 K, and 15.2% for LCMO (MnCO3) at 100 K in a 1 T magnetic field. [ABSTRACT FROM AUTHOR]

A sol–gel route based on tatrate/acetate was used to synthesize RuSr2(Gd2-xCex)Cu2O10-δ (x = 0.5 to 0.7) cuprate superconductors. A sample, with x = 0.6, was heated to 1050°C in oxygen flow for 24 h, followed by cooling at a rate of 1°C/min until it reached 100°C. The sample showed a single Ru-1222 phase with tetragonal symmetry. The lattice parameters for the sample were a = b = 3.863 Å and c = 28.57 Å. The onset transition temperature was 59 K, and the zero-resistance temperature was 40 K. [ABSTRACT FROM AUTHOR]

The formation of GdBa2Cu3O7-δ(Gd123) from metal oxalate precursor with average grain size less than 40 nm using the coprecipitation method is reported. The coprecipitated powders were heated at 900°C for 12 hours, pelletized and then sintered at 920°C for 15, 20 and 25 hours, respectively. All samples showed a dominant Gd123 phase with the orthorhombic structure. The amount of impurity phase Gd2BaCuO5(Gd211) can be controlled by varying the sintering time. This work shows that nano-sized oxalate powders produced via coprecipitation method can be an effective technique to synthesize high quality GdBa2Cu3O7-δ samples where the amount of (Gd211) can be controlled by varying the sintering duration. The percentage of Gd211 impurity decreased with increase in sintering time. This result is useful in utilizing the Gd211 phase as pinning center in enhancing the transport properties. [ABSTRACT FROM AUTHOR]

This paper reports the results of thermal diffusivity measurement on nano Ag added Bi2Sr2CaCu2O8-Agx (with x = 0–1.0) ceramics using an open-cell photoacoustic instrument. The thermal diffusivities were obtained by analyzing the phase of the photo-acoustic signal of thermally thick samples using Calderon's method as well as the analysis of the phase in thermally thick region. We found that the thermal diffusivity increases with the amounts of nano Ag. The values of thermal diffusivity obtained were between 0.01250 ± 0.00128 to 0.01606 ± 0.00230 cm2/s for Ag0 to Ag1.0. The electrical resistance versus temperature measurements showed a metal-like behavior for all samples. However, a metal-like transition was observed between x = 0.5 and 0.7 when results of thermal diffusivity and electrical resistance measurements were analyzed together with samples x ≥ 0.7 showing the metallic behavior. [ABSTRACT FROM AUTHOR]

Pb containing ruthenium-based superconducting cuprates Ru(Sr1.5Ca0.5)PbCu2O8 (Ru-1212 type) have been successfully synthesized through the sol–gel route. The optimum annealing temperature for the ruthenium-based cuprate superconductor was found to be 890°C. The crystal structure determined by X-ray powder diffraction method showed a single Ru-1212 type phase with tetragonal symmetry with lattice parameters a = b = 3.920 Å, and c = 11.76 Å. The Ru(Sr1.5Ca0.5)PbCu2O8 material showed onset temperature, Tc-onset at 35 K and zero resistant temperature, Tc-zero at 20 K. Pb together with the partial substitution of Sr with Ca lowered the formation temperature of the Ru-1212 type phase. [ABSTRACT FROM AUTHOR]

Ultrasonic longitudinal and shear velocity in superconducting ErBa[sub 2](Cu[sub 3-x]Zn[sub x])O[sub 7-δ] (x = 0, 0.01 and 0.05) have been measured using the pulse-echo-overlap method at frequency 5-10 MHz in the temperature range 80-300 K. Longitudinal velocity hysteresis and elastic anomaly were observed in the x = 0 sample. Similar hysteresis was not observed in the x = 0.01 and 0.05 samples. The characteristic Debye temperature and electron-phonon coupling constant were calculated. The absence of hysteresis for longitudinal velocity in the x = 0.01 and 0.05 samples may be due to the spin correlation at the CuO[sub 2] planes which affects the electron-phonon interaction. [ABSTRACT FROM AUTHOR]