Rare-earth doped yttria and scandia sesquioxides have been widely used as host materials for solid-state lasers and thermometric materials due to their high refractive index, wide bandgap, and high melting point. Both yttria and scandia crystallize in cubic bixbyite structure under ambient conditions with luminescence active trigonal-prismatic (C2) cation sites. The smaller Sc3+ ions have been shown to enhance the crystal field, modifying the allowed optical transitions. Despite their similarities, the formation of Y2-xScxO3 (YScO) nanocrystals does not readily occur under standard wet-chemical methods which generate high crystallinity nanoparticles ideal for luminescent applications. Here, we are investigating the synthesis and selective doping of YScO with Er to improve its upconversion performance. In this work, YScO nanoparticles were synthesized using co-precipitation and molten salt method with Er3+, in comparison with standard hydrothermal methods, as a photoluminescent probe to study the effect of site position and size on the upconversion performance. Co-doping the Y2O3 system with Sc3+ allows for manipulating lattice site sizes to concentrate Er3+ in the lower symmetric C2 sites. This formation of mixed YScO was confirmed systems using crystallographic (XRD/Raman) and spectroscopically (Photoluminescence). The optimum composition was determined to be Y1.75Sc0.25O3 based on upconversion luminescence intensity and decay lifetimes. Additionally, Judd-Ofelt analysis was performed to quantify luminescent efficiencies. The calculations showed that YScO:Er with Sc concentration less than 50% of (Y+Sc) have improved efficiency and intensity, and decreased site symmetry level, indicating the incorporation of small amounts Sc drives Er ions to occupy lower symmetry sites (C2) and reduces the overall site symmetry. Meanwhile, 5% of Yb codoped YScO:Er was found to significantly improve the luminescence intensity and red to green ratio instead of the commonly used concentration of 20%. Overall, this work allows controlling the spatial location of luminescence centers in the host material to optimize the luminescence performance of phosphor materials and develop a high-efficiency oxide material for high-temperature applications such as optical thermometers.

Spatial and structural effect to upconversion performance of Er3+ in Y2-xScxO3 hosts

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.