Synthesis of ErBa2Cu3O7-δ superconducting ceramic material via co precipitation and conventional solid state routes

High temperature superconductors (HTSC) of microcrystalline ceramic material ErBa2Cu3O7-δ (ErBCO) have been successfully synthesized via chemical co-precipitation (COP) using metal acetate precursors, and physical mixtures of oxides and carbonates, by conventional solid state route (SSR). The COP sample requires 27 hours for the heat treatment while the SSR sample needs 72 hours. We compare the superconducting properties of ErBCO produced from both methods. Resistivity versus temperature measurements (R-T) showed that all samples exhibit very good metallic behaviour. The transition temperature, TC(R=0) for the COP samples were was found to be at 91.4 K while it occurs at 90.9 K for the SSR sample sintered at 920°C. X-ray diffraction (XRD) data showed a single phase of an orthorhombic structure for all the samples. Scanning electron micrographs (SEM) showed grains of sizes ≤ 40μm were randomly distributed in all the highly compacted samples. However, the sample prepared via COP exhibited smaller pores in comparison to those in the SSR sample. COP method simplifies the preparation, and gives good quality sample with shorter time of preparation as compared to the quality of sample prepared by conventional solid state route

The effect of sintering temperature on the formation of (Tl, Cr)-1212 superconducting ceramic from coprecipitated oxalate precursors

TlSr1212 superconductors were synthesized by solid‐state reaction using Tl‐containing precursor powder prepared by coprecipitation of metal acetates with stoichiometric ratio based on Tl0.85Cr0.15Sr2CaCu2O7−δ composition. The samples were sintered at temperatures between 960 and 980°C for duration of 5 minutes. XRD patterns for samples sintered at 960°C showed formation of dominant 1212 phase in addition to minor 1201 phase and SrCO3 impurity. At this sintering temperature, the best superconducting behavior with TC(R=0) of 100 K was observed for the sample sintered at 970°C. SEM investigations on the sample revealed elongated grains which belong to 1212 phase with a slight directional grain alignment. The sample with sintering temperature of 960°C showed better grains connection as compared to the rest of the samples

Voltammetric Studies of DyBa2Cu3O7-δ (DyBCO) prepared via solid-state(SS) and co-precipitation (COP) technique

This paper describes a series of electrochemical measurements design to explore the reactivity of the oxide superconductor, DyBa2Cu3O7-δ (DyBCO). The reproducible voltammetry was obtained in the potential window of 1.0 V to -1.0 V vs Ag/AgCl reference electrode. DyBa2Cu3O7-δ was prepared via co-precipitation and conventional solid state technique. Parameters used in this study including the effect of potential cycling, scan rate, temperature and pH as well as chronoamperometry (CA) and chronocoulometry (CC). The electrochemical reduction and oxidation can be recognized easily by the solid-phase voltammetric technique. The cyclic voltammogram for DyBCO prepared in both techniques showed four major peaks attributed to first and second redox couple. The peaks are due to the redox reaction of Cu(NH3)42+ complex.The peak current is highly dependent upon the formation of the Cu(NH3)42+ complexwhich shows that the copper planes in the superconductor played major role inproducing the peaks observed in the voltammograms. A complex surface process was found in the redox reaction through the scan rate study. After thorough investigations, it was found out that DyBCO prepared in both techniques responses strongly under acidic(pH ≈ 2.00), high temperature (80oC) condition with slight differences in voltammetricbehaviors. The cyclic voltammetric behavior exhibited by both samples is found to depend greatly on the parameters used in this study. From CA and CC studies, theamount of charge, Q that was presence on the electrode surface is 17.0 µC/cm2 and 25.0µC/cm2 and diffusion coefficient, D is 4.6 x 10-6 cm2/s and 4.0 x 10-6 cm2/s for co-precipitation and conventional solid state technique, respectively. From the chronocoulometry (CC) measurement, the estimated mass of sample that was attachedon the glassy electrode is 65 ng and 96 ng for sample prepared via conventional solid state and co-precipitation technique, respectively

Abrasive stripping voltammetric (AbrSV) studies of ErBa2Cu3O7-δ superconductor synthesised via co-precipitation and solid state methods

The electrochemical analysis of ErBa2Cu3O7-δ (ErBCO) superconductor ceramic materials, adhered abrasively at a glassy carbon electrode surface placed in an aqueous media has been investigated by abrasive stripping voltammetry, AbrSV technique. ErBCO samples were prepared via co-precipitation (COP) and solid state (SS) method. Powder x-ray diffraction (XRD) patterns showed both samples to be single-phased 123 of an orthorhombic structure. Details studies on the reduction-oxidation of ErBCO involved the variation of scan rate, temperature and pH of electrolyte as well as chronoamperometry (CA) and chronocoulometry (CC). The voltammogram obtained for ErBCO prepared in both methods showed four major peaks attributed to first and second redox couples. The peaks are due to the redox reaction of Cu(NH3)42+ complex. The peak current is highly dependent upon the formation of the Cu(NH3)42+ complex which shows that the copper planes in the superconductor played major role in producing the peaks observed in the voltammograms. The voltammetric response of the ErBCO was found to depend greatly on the scan rate, pH and temperature. From CA and CC studies, the amount of charge, Q that was presence on the electrode surface is 4.7 μC/cm2 and 5.4 μC/cm2 and diffusion coefficient, D is 3.4 x 10-6 cm2/s and 4.0 x 10-6 cm2/s for solid state and co-precipitation method respectively

The influence of samarium doping in Bi1.6 (Pb0.4)Sr2- xSmxCa2Cu3Oy prepared by coprecipitation method

The influence of Sm doping on the phase formation, normal state properties and microstructure development of Bi-2223 superconductors was systematically investigated. Samarium was incorporated in the strontium site with x ranging from 0.00 to 0.30 prepared via coprecipitation technique. The four point probe measurements showed the loss in metallic behaviour for the samples with Sm doped above x=0.2. XRD results showed the decrease of the volume percentage of the 2223 phase followed by increasing in the density of the lattice. The SEM micrographs showed the decrease in the grain size for all samples containing samarium. The temperature dependence of ac susceptibility data shows the shifting towards lower temperature as the Sm concentration increases presence of low Tconset phase. The imaginary component, χ”, shows a decrease in the intergranular coupling peak, Tp, towards lower temperature as the Sm concentration increases. Samarium did not enhance the Tc(R=0) but gradually decreases its value from 102. K to 52 K for x=0.00 to x=0.20 respectively

Magnetotransport properties of La0.67Ca0.33MnO3 with different grain sizes

The magnetotransport and magnetoresistive (MR)properties of manganese-based La0.67Ca0.33MnO3 perovskite with different grain sizes are reported. The electrical resistivity was measured as a function of temperature in magnetic fields of 0.5 and 1 T. The insulator–metal transition temperature, TIM, shifted to a higher temperature with the application of the magnetic field. In zero field, TIM is almost constant (∼271 K) for all samples except for the sample with the largest grain size, where TIM = 265 K. The temperature dependence of resistivity was fitted with several equations in the metallic (ferromagnetic) region and the insulating (paramagnetic) region. The density of states at the Fermi level, N(EF), and the activation energy of electron hopping were estimated by fitting the resistivity versus temperature curves. The ρ–T 2 curves are nearly linear in the metallic regime, but the ρ–T 2.5 curves exhibit a deviation from linearity. The variable range hopping model and small polaron hopping model fit the data well in the high-temperature region,indicating the existence of the Jahn–Teller distortion that localizes the charge carriers. MR was found to increase with an increase in the magnetic field, an effect which is attributed to the intergrain spin tunneling effect

Phase formation of REBa2Cu3O7−δ (RE: Y0.5Gd0.5, Y0.5Nd0.5, Nd0.5Gd0.5) superconductors from nanopowders synthesised via co-precipitation

Phase formation of REBa2Cu3O7−δ (RE: Y0.5Gd0.5, Y0.5Nd0.5, Nd0.5Gd0.5) superconductors synthesised via co-precipitation (COP) method were investigated by thermogravimetric analysis (TGA), differential thermal analysis (DTA) and X-ray diffraction (XRD) analysis. All samples showed identical thermal decomposition behaviour from the thermogram in which 5 major weight losses were observed. However, XRD of the samples at different heat treatment temperatures showed different diffraction patterns indicating different thermolytic processes. Meanwhile, transmission electron microscopy and surface area analysis revealed that the powders obtained from COP have particle sizes ranging from 7 to 12 nm with relatively large surface area. Molar ratios of prepared samples obtained were near to the theoretical values as confirmed by elemental analyses using X-ray fluorescence (XRF). The TC(R=0) for sintered YGd, YNd and NdGd were 87 K, 86 K and 90 K, respectively. Surface morphological study via scanning electron microscope showed the structures of samples were dense and non porous

Study on the superconducting properties of Mn substituted YBCO

We have performed a study on the superconducting properties of Y1-xMnxBa2Cu3O7-δ with various Mn doping (x = 0.00, 0.25, 0.30, 0.35, 0.40 and 0.45). All of the samples displayed significant Meissner effect. XRD patterns indicate the existence of unknown peaks belonging to the impurities. A decrease in grain size as the concentration of Mn increases was observed from the SEM micrographs. The resistivity results showed the shifting in TC(R=0) towards low temperature as the Mn concentration increases

Characterization of TiO2-chitosan/glass photocatalyst for the removal of a monoazo dye via photodegradation-adsorption process

In this paper, the newly explored TiO2–Chitosan/Glass was suggested as a promising alternative material to conventional means of wastewater treatment. Characterization of TiO2–Chitosan/Glass photocatalyst was studied with SEM-EDX, XRD, and Fourier transform infrared spectroscopy (FTIR) analysis. The combination effect of photodegradation–adsorption process for the removal of methyl orange (MO), an acid dye of the monoazo series occur promisingly when four layers of TiO2–Chitosan/Glass photocatalyst was used for MO removal. Approximately, 87.0% of total MO removal was achieved. The reactive –NH2, –OH, and metal oxide contents in the prepared photocatalyst responsible for the photodegradation–adsorption effect were confirmed by FTIR study. Similarly, MO removal behavior was well supported by SEM-EDX and XRD analysis. Significant dependence of MO removal on the TiO2–Chitosan loading can be explained in terms of relationship between quantum yield of photocatalytic reactions and photocatalyst structure/activity. Hence, the research work done thus far suggests a new method, having both the advantages of photodegradation–adsorption process in the abatement of various wastewater pollutants

Characterization of newly prepared TiO2-chitosan/glass for the removal of a monoazo dye via the combination effect of photodegradation-adsorption

The newly prepared TiO2-Chitosan/Glass is a promising alternative/complementary method to conventional means of wastewater treatment. Characterization of TiO2-Chitosan/Glass photocatalyst was studied with SEM-EDX, XRD, and FTIR analysis. The combination effect of photodegradation-adsorption process for the removal of methyl orange (MO), an acid dye of the monoazo series occur promisingly when 4 layers of TiO2-Chitosan/Glass photocatalyst was used for MO removal. FTIR study had confirmed the reactive –NH2, -OH, and metal oxide contents in the prepared photocatalyst responsible for the photodegradation-adsorption effect. Similarly, MO removal behavior was well supported by SEM-EDX and XRD analysis. A marked dependence of MO removal on the TiO2-Chitosan loading was observed and discussed. The research work done thus far suggests a new method, having both the advantages of photodegradation-adsorption process in the abatement of various wastewater pollutants