Controlling the morphology of nanocrystalline Y(OH)${}_3$ powders synthesized by microwave-hydrothermal route and effect of annealing

Y(OH)${}_3$ is the main precursor material to inherit desirable morphologies for Y${}_2$O${}_3$. The Y(OH)${}_3$ and Y${}_2$O${}_3$ are an important substitution for luminescent matrix and useful in temperature sensing applications. Nanostructured and phase-pure Y${}_2$O${}_3$ is also used as an essential dispersoid for the oxide dispersion strengthened steels which are candidate materials for future fast breeder reactors. In the present work, the nanostructured Y(OH)${}_3$ is prepared indigenously by the microwave-hydrothermal route which is appropriate to provide-uniform heating to the material and the hydrothermal-pressure environment plays a major role in the growth kinetics of morphology. The synthesis was carried out at various microwave powers of 700 and 800 W to obtain the different morphologies of tubular and rod-like structures, respectively. The morphology is attributed to the influence of heat-rate on the variation in hydrothermal pressure governed by microwave power. The morphologies remain the same on calcination 800 °C. As-synthesized powder samples showed hexagonal structure whereas the cubic structure was observed for those calcined at 800 °C for both morphologies. The hydroxide vacancies lead to form a cubic structure that has a larger unit cell. The yttrium oxides showed lattice compaction for the rod-like structure but yttrium hydroxides did not depict any difference in the lattice for the tubular and rod-like morphologies. Likewise, Raman spectroscopy analysis confirmed the formation of hexagonal and cubic phases for the as-synthesized and calcined nanopowder samples, respectively.