Articles written in Bulletin of Materials Science

• Superconductivity behaviour of screen-printed LnBa2Cu3O7 (Ln=Eu, Y) films

Thick films of the highTcsuperconducting oxides, LnBa2Cu3O7, Ln = Eu, Y, have been fabricated by screen printing on alumina and SrTiO3 substrates. Conditions for optimum superconductivity behaviour of the films have been established.Tconset varies from 90–94 K for all the films but zero resistance was observed only in a few cases.

• Oxygen-enrichment of YBa2Cu3 YBa2Cu3O7-δ using the fluidization techniqueusing the fluidization technique

The oxygen-deficient phase of the highTc superconductor, YBa2Cu3O7, was oxygen-enriched using the fluidization technique to give good superconducting properties. The normal method of oxygen treatment at 900°C for 24 h and at 600°C for 24 h has been reduced to just one treatment at 600°C for 12 h by the fluidization technique to achieve almost the same strength of superconducting signal for the YBa2Cu3O7 powder, which establishes the attractiveness of the latter route for the large-scale preparation of superconducting material. The particle sizes were in the range 0–90, 90–180 and 180–420 µm. The fluidized particles were crystalline with orthorhombic distortion.Tconset, estimated using the a.c. magnetic susceptibility method, was 91·3 K. The volume fraction of superconducting material in the product was 83·7–85·3%, one of the highest values reported so far for YBa2Cu3O7.

• Effect of oxide additives on the properties of high temperature superconductor, YBa2Cu3O7

The effect of oxide additives-CuO, SiO2, Y2O3, Bi2O3 and ZnO in 1–10 mol% on the sintering and superconducting properties of YBa2Cu3O7 was studied. SEM studies indicated improvement of grain size and interconnectivity due to the additives, the best results being obtained with Bi2O3, SiO2 and Y2O3. The superconducting transition temperature is unaffected (92±2 K) even with 10 mol % of the additives. ZnO, however, decreases theTc as expected.

• Studies on Li-doped Ca0·85Sr0·15CuO2: the prototype of cuprate family of oxide superconductors

The layer-type compound, Ca0·85Sr0·15CuO2, which is the prototype of the cuprate family of highTc oxide superconductors is an electronic insulator, and has a low ordered moment at 300 K indicating that Cu2+ ions are highly correlated. Doping with lithium (up tox=0·15) decreases the room temperature resistivity drastically (from 103 ohm·cm to 0·6 ohm·cm) but metallic behaviour is not induced below 300 K. The magnetic moment on Cu2+ remains low but our studies did not show any antiferromagnetic ordering below 300 K in any of the Li-doped phases.

• Superconductivity studies on Tl-Th-Sr-Ca-Cu-O system

Superconductivity with a maximumTc, zero of 58 K forx &gt; 0·75 has been observed in a nominal starting composition, ThxTl2Sr2Ca2Cu3Oy. X-ray data show that the 1212 phase gets stabilized due to part substitution of Th at the Tl-site forx⩾0·25; however,Tc is low forx&lt;0·75.

• Effect of oxide additives onTc behaviour of Bi2·1Sr1·93Ca0·97Cu2O8 system

We have carried out studies on the effect of oxide additives (Ca0·85Sr0·15CuO2, BaBiO3 and BaPbO3) on Bi-2212. Compositions up to 6 mole% of all the additives have been prepared and characterized by XRD, resistivity and ac susceptibility techniques. XRD studies indicate that all the materials are single phase. Resistivity and ac susceptibility studies indicate enhanced granular behaviour with the oxide additives. Low temperature (400°) sintering results in degradation of the Bi-2212 phase in the presence of the additives.

• Photoelectrochemical studies on the mixed oxides, A6Nb8Ti2O30 (A = Ba, Sr)

The photoelectrochemical behaviour of oxide bronzes of the type A6Nb8Ti2O30 (A = Ba. Sr) has been studied. They show good photoactivity with photopotentials of the order of 700–800 mV. The flat band potential has been estimated to be − 0·9 V vs SCE. The band gap estimated from the spectral response is 3·1 eV.

• Recent advances in 2 : 17 and 3 : 29 permanent magnet materials

The structural and magnetic properties of 2 : 17 compounds, their nitrides and carbides and the recent development of the novel 3 : 29 compounds are discussed.

• Eu(III)-doped barium tellurooxyphosphate phosphor with orange-red emission

Eu$^{3+}$ photoluminescence (PL) is studied in the tellurooxyphosphate, Ba$_2$TeO(PO$_4$)$_2$, host. A series of phosphor compositions with varying concentrations of Eu$^{3+}$ dopant in Ba$_2$TeO(PO$_4$)$_2$ are synthesized by high temperature solid-state reaction and the PL spectra are recorded. Under 395 nm wavelength excitation, the emission spectrum shows a single peak corresponding to the non-degenerate transition, ${}^5$D$_0$ $\to$ ${}^7$F$_0$ indicating that Eu$^{3+}$ preferentially occupies a singlecrystallographic site. The peak due to the degenerate hypersensitive ${}^5$D$_0$ $\to$ ${}^7$F$_2$ electric dipole transition of Eu$^{3+}$ in theemission spectrum indicates that the site occupied by Eu$^{3+}$ in the tellurooxyphosphate host lattice is non-centrosymmetric. The CIE coordinate values are $x = 0.61$ and $y = 0.34$ and are found to be close to the values of the reference phosphor Y$_2$O$_3$:Eu$^{3+}$.

• # Bulletin of Materials Science

Volume 43, 2020
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Continuous Article Publishing mode

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019