Gd0.745Y1.255O3 and Yb1.4Y0.6O3 Mixed Rare-earth-yttrium Oxides Nano-powders: Synthesis, Characterization, Particle-size Distribution and Optical Properties

Gd0.745Y1.255O3 and Yb1.4Y0.6O3 nano-powders of mixed rare-earth-yttrium sesquioxides (diluted magnetics) were successfully synthesized via a simple co-precipitation method using rare-earth-nitrate salts as cation precursors and followed by a 4 hour heat-treatment at various temperatures (600 °C, 800 °C and 1000°C) for material crystallization. Experiments demonstrated the role of pH on the “co-precipitation” synthesis of Gd0.745Y1.255O3 and Yb1.4Y0.6O3 nano-powders. The pH values were adjusted by adding NaOH which, as a precipitating agent, has a key role in this process. The obtained nano-powders were characterized by X-ray powder diffraction; their morphologies were analyzed by scanning electron microscope SEM, their average sizes were calculated using Scherrer formula, and their optical properties were studied using UV-Vis spectrophotometer with Tauc plot estimation to determine the band-gap energy. The influence of heat treatment, on the morphology and crystallite sizes of Gd0.745Y1.255O3 and Yb1.4Y0.6O3 nano-powders, was studied. The results indicated that the agglomeration of particles was favored by hydroxide precipitation, one of many other factors, including temperature and calcination time, that influence the quality of Gd0.745Y1.255O3 and Yb1.4Y0.6O3 nano-powders according to the SEM images, while the XRD analysis showed that crystallinity increased with an increase in calcination temperature. The study of particle-size distribution at different calcination temperatures indicated that the Grain-size increased from ~42 nm to ~100 nm for Gd0.745Y1.255O3 and from ~13 nm to ~50 nm for Yb1.4Y0.6O3 as the calcination temperatures increased, this influence also the optical band-gap which found to be decreasing from 4.22 to 3.95 eV when the particle sizes increasing for Yb1.4Y0.6O3.