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P. Puviarasu

Abstract

The surface morphological characteristics of wet chemical etched GaN layers grown at different temperatures on (0 0 0 1) sapphire substrates by Chloride-Vapor Phase Epitaxy (Cl-VPE) have been studied using optical microscope. Significant surface morphology changes have been observed in correlation to the growth temperature and etching time. Also optical properties of the as grown and high-energy silicon (Si) ion irradiated gallium nitride (GaN) epilayers were studied using monochromatic ellipsometry. The effect of ion fluences on the refractive index of the GaN has been investigated and it has been found to decrease with an increase of ion fluence. This decrease is attributed to irradiation-induced defects and polycrystallization which plays an important role in determining the optical properties of silicon (Si) ion irradiated GaN layers.

Open access

A. Senthil Kumar, R. Balaji, P. Puviarasu and S. Jayakumar

Abstract

Gadolinium doped barium cerate (BCG) electrolytes Ce0.8Gd0.2O1.9 + xBaO (x = 0.1 and 0.4) were prepared by wet chemical method for the use in solid oxide fuel cells operating at intermediate temperatures (600 °C to 800 °C). The as-prepared powder sample was calcined at 900 °C. The calcination temperature was identified using differential scanning calorimetry (DSC) analysis. The orthorhombic perovskite phase formation was confirmed by XRD analysis. From TEM results, the particle size was found to be about 32 nm which is in a good agreement with XRD results. BCG nanoparticles were formed at lower sintering temperature due to using microwave furnace. By reducing the sintering temperature of solid electrolyte through microwave technique, the percentage of barium loss was successfully reduced and the prepared electrolyte can be a good choice for solid oxide fuel cells operating at intermediate temperatures.