Synthesis and structural characterisation of Y2Ti2O7 using microwave hydrothermal route

Abstract

In the present work, we established an ex-situ procedure to synthesize Y2Ti2O7 nanopowder using the microwave-hydrothermal technique followed by conventional calcination treatment. This powder is otherwise synthesized by in-situ through a reaction between Y2O3 and Ti in a steel matrix for the production of oxide dispersion strengthened (ODS) steels. The hydrothermal synthesis was involved of chemical reactions in high pressure and high temperature environment. The as synthesized powder was identified as mixed-phase of both Y(OH)3 and TiO2 from the X-ray diffraction (XRD) analysis. This work was focused on phase formation of pyrochlore Y2Ti2O7 powder with respect to calcination treatment. On calcination at 850 °C, the mixed phase of cubic-Y2O3, anatase-TiO2 and cubic-Y2Ti2O7 were identified. Pyrochlore structured-Y2Ti2O7 was observed on calcination temperatures 950 and 1050 °C. This was attributed to the structural evolution with calcination to form single phase Y2Ti2O7. Morphology variation is investigated using scanning electron microscopy. The as-synthesized nanopowder showed a mixture of rod like and particle like morphologies. Presence of these morphologies attributed to the formation of typical of hydroxide phases during the powder synthesis. The morphologies were modified to uniform nanoclusters by forming cubic-Y2Ti2O7 phase when it was calcined at 950 and 1050 °C respectively. The structural phase was also verified using high resolution transmission electron microscopy (HRTEM) and Raman spectroscopic studies. The oxide was found to be stable till 1200 °C from DSC and XRD studies.