Study of structure and relaxation dynamics of some oxygen ion conductors

This thesis is devoted to the study of the structure and relaxation dynamics in some oxygen ion conducting materials. Oxide based electrolytes and cathode/anode materials or fast oxide ion conductors have considerable applications in solid oxide fuel cell, oxygen gas sensors and solid state based devices. Some crystallographic families have shown high oxygenion mobility. Recent study on lanthanum molybdenum oxide (LAMOX), strontium and magnesium doped lanthanum gallate (LSGM) and doped yttria stabilized zirconia (YSZ) compounds have indicated their high applicability in intermediate temperature (600 - 800 C) solid oxide fuel cell (IT-SOFC). The structure and ion dynamics of doped La2Mo2O9 ceramic compounds have been studied in detail. The crystalline nature of these materials has been con rmed by X-ray di raction. The formation of doped materials in these samples has also been con rmed using scanning and transmission electron microscopy. The thermal property of these samples has been studied using thermogravimetry analysis (TGA). The modi cation of lattice structures with addition of di erent dopants has been investigated using Fourier Transform Infrared (FTIR) and Raman Spectroscopy. Electrical measurements of the samples have been performed using a precision RLC meter in a wide temperature range of 300 K - 1200 K and in the frequency range of 10 Hz - 3 GHz. The dc conductivity and the activation energy have been correlated with the structural modi fication of these oxide samples. The electrical measurements have been analyzed in the framework of conductivity, dielectric and electric modulus formalism. The parameters namely, the hopping frequency, concentration of charge carriers and the frequency exponent have been determined. The dielectric formalism has been used to study the non-Debye relaxation. The electric modulus formalism has been used to study the stretched exponent behavior. Scaling properties of the conductivity and modulus spectra have been investigated to gain insights into the oxygen ion dynamics in these materials.The research was carried out under the supervision of Prof. Aswini Ghosh of Solid State Physics division under SPS [School of Physical Sciences]The research was conducted under DST INSPIRE Fellowshi