Effects of magnetic nanoparticles dysprosium oxide (Dy2O3) addition on electrical properties of (Bi,Pb)-2223 high TC superconductors / Nurul Raihan Mohd Suib

In this study, co-precipitation technique has been performed in preparation of Bi1.6Pb0.4Sr2Ca2Cu3O10 ceramic superconductor. In order to change the electrical properties of the superconductor powder, magnetic nanoparticles Dy2O3 were added with nominal composition ranging from x=0 to x=0.10 wt% at different sintering time. The ultrafine superconductor powder produced by co-precipitation method has increased the diffusion reaction and shortened the heat treatment procedure for the sample preparation. These lead to better superconducting properties as compared to the samples prepared by conventional solid state technique where its diffusion reaction require s a high temperature and long sintering hour, it is laborious , time intensive and contaminated products may be occurred. Co-precipitation method has proved it high TC at 102 K when sintered for 24 hours. Absolutely, this time taken probably unachieved at same sintering time to solid state technique probably it’s taken more longer time to have the same TC. From this study the resistivity measurement has been done for all samples, and showed that Tc(R=0) from 100-109 K and Tc-onset 108-117 K. The TC achieved showed the high TC when it is more than 100 K. From XRD analysis, samples showed that the grain and formation of phase is more dominated by Bi-2223 phase rather than Bi-2212 when varied of wt% addition magnetic nanoparticles Dy2O3 to all samples. Results from XRD shows the peak of DY2O3 was not detected. It implied that the magnetic nanoparticles of DY2O3 was incorporated in the crystalline structure, However in EDX shows the distribution of magnetic nanoparticles DY2O3 so it showed the existed of DY2O3 in samples. From SEM analysis, showed also the large flaky of (Bi,Pb)-2223 structure was randomly distributed. The effect of magnetic nanoparticles DY2O3 addition on superconducting material s will alter the electron pairing mechanism and affected the flux pinning strength. With prolonged the sintering time, it shows an improvement in superconducting electrical properties. The optimum sintering time is 48 hours, where the highest JC was obtained at 18.82±0.86 A/cm2 at 30 K

Effect of heat treatment condition on the phase formation of YBa2Cu3O7-δ superconductor

Polycrystalline samples with the nominal composition YBa2Cu3O7-δ (Y-123) were prepared using the co-precipitation method. The effect of the calcination process (single and multiple calcinations) on the samples was investigated by using the four-point temperature-resistance measurement, x-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM). This study is divided into two parts. For the first part, the obtained oxalate powder underwent two calcination processes at 900 °C for 12 h and 900 °C for 24 h, respectively. Then, the powders were pressed into pellets and sintered at 920 °C for 15 h with oxygen flow during the entire heat treatment. In the second part, only one calcination process was undertaken at 900 °C for 24 h before the sintering process in oxygen flow at 920 °C for 15 h. From the XRD patterns, all of the peaks were indexed to the Y-123 phase showing that this superconducting phase was already formed after the first calcination. The volume fraction of Y-123 of the samples with single calcination process was higher compared to multiple calcination processes. From the temperature-resistance measurement, all the samples showed metallic behavior in the normal state and a superconducting transition to zero resistance. The superconducting transition temperature, Tc, for the samples prepared in a single calcination process is higher than that of the multiple calcination processes

Sifat elektrik dan kerentanan arus ulang alik superkonduktor Bi(Pb)-Sr-Ca-Cu-O dengan penambahan In2O3

Kesan penambahan In2O3 terhadap superkonduktor (Bi1.6Pb0.4)Sr2Ca2Cu3O10 (In2O3)x (x = 0- 0.1 peratus berat) telah dikaji. Pencirian yang dijalankan ialah pembelauan sinar-X, mikrostrukur, rintangan elektrik, kerentanan arus ulang alik dan ketumpatan arus genting antara butiran. Suhu genting mula, Tc mula dan suhu genting sifar, Tc sifar adalah tertinggi bagi sampel x = 0 iaitu Tc mula = 112 K dan Tc sifar = 90 K. Corak pembelauan sinar-X menunjukkan peratus isi padu fasa (Bi1.6Pb0.4)Sr2Ca2Cu3O10 (Bi-2223) dan (Bi1.6Pb0.4)Sr2CaCu2O8 (Bi-2212) adalah hampir sama untuk semua sampel. Pengukuran kerentanan ulang alik telah dijalankan pada frekuensi 295 Hz dan medan magnet H = 5 Oe. Dua peralihan pada kerentanan ulang alik bagi x = 0 menandakan kewujudan fasa Bi-2223 dan Bi-2212. Suhu pada puncak kehilangan tenaga, Tp untuk kerentanan khayal, χ” adalah tertinggi (74 K dan 104 K) untuk x = 0. Penambahan In2O3 telah menyebabkan Tp beranjak kepada suhu lebih rendah dan ini menunjukkan fluks magnet menembusi antara butiran pada suhu yang semakin menurun apabila In2O3 ditambah. Lengkung puncak Tp juga melebar apabila In2O3 ditambah. Ini menunjukkan gandingan antara butiran yang semakin lemah dan tenaga pengepinan fluks yang menurun. Ketumpatan arus genting antara butiran Jc(Tp) telah diukur menggunakan model Bean dan nilainya adalah antara 16 hingga 20 A cm-2 bagi semua sampel. Satu model skematik arus aruhan bagi bahan polihablur yang mengandungi dua fasa superkonduktor dengan pecahan isi padu yang sama tetapi suhu genting yang berlainan dibincangkan

Superconductivity of REBa2Cu3O7-δ (RE= Y, Dy, Er) Ceramic Synthesized Via Coprecipitation Method

The REBa2Cu3O7-δ (RE= Y, Dy, Er) superconducting ceramics have been prepared via coprecipitation(COP) method from nearly saturated solutions of metal acetates and 2- propanol solution of oxalic acid. The metal oxalates powders were subjected to thermal treatment of 12 hours calcination at 900oC. The pelletized powder was sintered for 15 hr at 920oC. All samples showed a single step transition in the R-T curves. The TC(R=0) for samples Dy123, Y123and Er123 and were 93 K, 91 K and 90 K, respectively. XRD data showed single phase of an orthorhombic structure for all samples. SEM micrographs showed large grain sizes that are randomly distributed. These results showed that COP method using metal oxalates starting powders is very effective to synthesize high quality superconductors and shorten the sintering time required due to the formation of sub micron oxalate powders

AC susceptibility and electrical properties of rare-earth- and alkali metal-substituted (Tl0.7M0.3)Sr2CaCu2O7 with M = Er, Gd, La, Na, K and Rb

The effects of rare-earth elements M = Er, Gd and La, and alkali metals M = Na, K and Rb substitution on (Tl0.7M0.3)Sr2CaCu2O7 (Tl-1212) are reported. The rare-earth elements were chosen by considering the ionic radius, i.e., from the smallest (Er+3) to the largest (La+3) ion. The samples were prepared via the solid-state reaction method. X-ray diffraction patterns showed the presence of major Tl-1212 and minor Tl-1201 and Ca0.3Sr0.7CuO2 phase in almost all samples. The resistance versus temperature curves for the rare-earth-substituted samples showed onset temperature between 87 and 90 K and zero resistance temperature between 69 and 81 K. Alkali metal substitutions exhibited Tl-1212 phase but showed no superconducting transition although the electrical resistivity was much lower than the rare-earth-substituted samples. AC susceptibility measurement showed superconducting transition Tcχ, between 59 and 80 K for the rare-earth element-substituted samples. The average grain size, the transition temperature, Tcχ and the peak temperature Tp of the imaginary part of the susceptibility χ″ decreased as the ionic radius of the rare earths was reduced