Investigations on the synthesis and characterization of some rare earth oxide nanostructures and mesocrystals

Abstract

Rare-earth (RE) oxides have been widely used in high-performance luminescent, magnetic, catalytic, and other functional devices due to their unique electronic, optical and chemical characteristics arising from 4f electrons. Mesocrystals have received rapidly increasing attention since they were first proposed as a new class of ordered nanoparticle superstructures by Cölfen. Mesocrystals not only possess the properties of nanoparticles in microscale, but also exhibit unique characteristics or improved properties. Investigations have been carried out on the growth kinetics and morphological evolution of CeO2 nanoparticles synthesized by mixed solvothermal route. The as-dried sample was subjected to calcination at 400°C, 500°C and 600°C for 2h and the effect of calcination temperature on the growth kinetics and morphology of the nanoparticles was studied. X-ray diffraction (XRD) studies showed that the calcinated samples exhibit phase pure cubic fluorite structure, which was further confirmed by Raman studies. The possible formation mechanism has been discussed based on the experimental results. PL analyses demonstrate that the RE ions (Ce3+, Sm3+ and Gd3+) uniformly substitute Dy3+ sites in Dy2O3 lattice and hence influence the optical properties. C14TAB assisted CeO2 and Pr6O11 mesocrystals were synthesized via wet-chemical route and their self-assembly mechanism has been investigated. XRD, SEM, AFM, HRTEM, EDS, FTIR, Raman, UV-Vis and PL spectroscopy were employed to characterize the crystal phase, morphology, chemical composition and optical properties of CeO2 and Pr6O11 mesocrystals. The experimental results showed that the product possesses mesocrystal structure with self-assembly architecture in the presence of C14TAB as template. A possible formation mechanism of CeO2 and Pr6O11 mesocrystals is proposed on account of aggregation of nanoparticles along with the epitaxial orientation. The prepared samples exhibit a very strong near band edge emission with weak defect emissions. newline