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Rare-earth titanate pyrochlores of the general formula R₂Ti₂O₇ have attracted considerable interest owing to their flexible structural chemistry and multifunctional physical properties. In this work, dysprosium titanate (Dy₂Ti₂O₇) and samarium titanate (Sm₂Ti₂O₇) were successfully synthesized using the sol-gel method and subsequently calcined at 1000 0C to obtain phase-pure pyrochlore samples. The structural properties were investigated by X-ray powder diffraction (XRD) with Rietveld refinement, confirming the formation of a single-phase cubic pyrochlore structure (space group Fd3̄m) for both samples. Refined lattice parameters were consistent with the expected systematic variation with rare-earth ionic radius, with Dy₂Ti₂O₇ exhibiting a smaller unit cell than Sm₂Ti₂O₇ in accordance with the lanthanide contraction. Additionally, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the morphology, chemical composition, particle size, and microstructural features of the synthesized powders. SEM analysis revealed agglomerated particles with morphology with no additional element, while TEM confirmed nanoscale crystallite dimensions and provided lattice fringe spacings consistent with the pyrochlore crystal structure. The optical properties were examined using UV-visible diffuse reflectance spectroscopy, from which optical bandgaps were obtained using Tauc plot analysis. Both samples behave as wide-bandgap insulators, with Sm₂Ti₂O₇ exhibiting a comparatively narrower band gap relative to Dy₂Ti₂O₇, attributed to differences in the rare-earth 4f electronic structure and its hybridization with the O 2p valence band. This work reports the systematic insight into the relationship between rare-earth identity, crystal structure, microstructure, and optical response across the R₂Ti₂O₇ pyrochlore group, with a potential relevance to optical device applications.
| Apply for student award at which level: | PhD |
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