Jijimon K. Thomas

Rare-Earth Barium Niobates:* A New Class of Potential Substrates for YBa2Cu3O7-δ Superconductor

A class of complex perovskites REBa2NbO6 (where RE=Pr, Nd, Sm and Eu) have been sintered as single phase materials having a high sintered density and stability, for their use as substrates for YBa2Cu3O7-δ superconductors. The structure of these materials was studied by X-ray diffraction technique and all of them were found to be isostructural having a cubic perovskite structure. These newly developed materials do not react with YBa2Cu3O7-δ superconductors even after annealing 1:1 volume mixture at 950° C for 15 h. The presence of REBa2NbO6 upto 20 vol% in the YBa2Cu3O7-δ–REBa2NbO6 composite did not show any deterimental effect on the superconducting transition temperature of YBa2Cu3O7-δ. Dielectric constant and loss factor of REBa2NbO6 were found to be in the range suitable for their use as substrates for microwave applications. Superconducting YBa2Cu3O7-δ thick films screen-printed on these new substrates gave a zero transition temperature T c0≈92 K and current density≈2×105 A/cm2 at 77 K.

Band gap tuning and improved optical properties of ZrO2-SnO2 nanocomposite thin films prepared by sol-gel route

Transparent nanocomposite ZrO2-SnO2 thin films (0.1/0.9 (ZS19), 0.5/0.5 (ZS55) and 0.9/0.1 (ZS91) of ZrO2/SnO2 were prepared by sol-gel dip-coating technique. X-ray diffraction (XRD) pattern of ZS55 shows a mixture of three phases: tetragonal ZrO2 and SnO2 with the crystal sizes of 11 nm and 8 nm, respectively and orthorhombic ZrSnO4 with the crystal size of 14 nm. Scanning electron microscopy (SEM) observations show that microstructure of ZS55 consists of isolated SnO2 particles dispersed in ZrO2 matrix. An average transmittance greater than 85% (in UV–visible region) is observed in ZS55 thin film. The band gap of the nanocomposite thin film decreases from 5.33 to 4.24eV with increase in Sn concentration which can be directly employed in extending the range of tunability of the band gap. Photoluminescence (PL) spectra reveal an intense emission peak at 426nm in ZS55 sample which indicate the presence of oxygen vacancies in ZrSnO4.

Electrical and optical properties of nanocrystalline RE–Ti–Nb–O6 (RE = Ce, Pr, Nd and Sm) electronic material

Nano-crystalline RETiNbO6 (RE = Ce, Pr, Nd and Sm) is successfully synthesized through the solution combustion technique. The XRD analysis revealed that the materials have orthorhombic aeschynite structure with space group Pnma. The particle size determined from XRD and TEM shows that the samples are nano-crystalline. Structure is confirmed by the analysis of FT-Raman, the fourier transform infrared spectra and surface morphology by SEM micrograph. The optical properties, dielectric characteristics at radio frequency range and complex impedance of the system are also studied. Percentage of rare earth in each compound, sintering temperature and density achieved are calculated. The UV–Vis spectra show that the materials can be used as a protective material from UV radiation due to high absorbance in that region. These compounds show strong emission in violet and green regions in the photoluminescence spectrum. The compounds are useful in communication systems due to low dielectric loss and high dielectric constant. The high ionic conductivity suggests that the material can be used as electrolyte in solid oxide fuel cells.

Enhanced infrared transmission characteristics of microwave-sintered \(\hbox {Y}_{2}\hbox {O}_{3}\)–\(\hbox {MgO}\) nanocomposite

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Electrical and dielectric properties of ZnO and CeO2 doped ZrTi2O6 ceramic

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Enhancement of photoluminescence emission intensity of zirconia thin films via aluminum doping for the application of solid state lighting in light emitting diode

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Photoluminescence and dielectric properties of LnTiTaO6 (Ln = Ce, Pr, Sm) polycrystals

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