Enhanced red and near-infrared upconversion luminescence properties in CaSc2O4 microcrystals

CaSc2O4 co-doped with Yb/Er, Yb/Tm was successfully prepared through a high-temperature solid-state method. The enhanced red and near-infrared upconversion luminescence intensities in CaSc2O4 co-doped with Yb/Er, Yb/Tm were observed. As the increase of Ca2+ ion doping concentration, the crystal phase evolved from cubic Sc2O3 to orthorhombic CaSc2O4, then to cubic CaO. When Ca2+ ion doping concentration is about 40 mol%, CaSc2O4 co-doped with Yb/Er has the maximum red emission intensity (666 nm) which is increased by 39.5 times than that of Sc2O3 microcrystals (MCs). Similarly, the maximum near-infrared emission intensity (807 nm) in CaSc2O4 co-doped with Yb/Tm is enhanced by 9 times than that of Sc2O3 MCs when Ca2+ ion doping concentration is about 40 mol%. They are in accordance with that Er3+ ion and Tm3+ ion exhibit the longest luminescence lifetime in CaSc2O4 MCs than that in Sc2O3 and CaO MCs.