A Novel Upconversion Emission Material Based on Er3+ - Yb3+ - Mo6+ Tridoped Hydroxyapatite/Tricalcium Phosphate (Ha/β-Tcp)

In this paper, a novel material based on Er-Yb-Mo tri-doped HA/beta-TCP phosphor for intense green upconversion (UC) emission was successfully synthesized by solid-state reaction method. X-ray diffraction (XRD) measurements verified that the materials including a trace amount of HA phase has a hexagonal structure and main beta-TCP phase has a rhombohedral structure, which is controlled by the doped ions. Under excitation wavelength of 976 nm laser diode, the HA/beta-TCP:Er-Yb-Mo phosphor showed strong green UC emission band at 520/556 nm and weak red emission band at 656 nm which are attributed to (H-2(11/2), S-4(3/2)) - I-4(15/2), F-4(9/2) - I-4(15/2) transition of the Er3+ ion, respectively. Remarkably, compared with the sample without Mo6+, the green emission intensities increased similar to 650 times was achieved by using Er3+-Yb3+-Mo6+ doped phosphor. The high efficiency of the UC can be attributed to novel energy transfer process from vertical bar F-2(7/2), T-3(2)> state of Yb3+ - MoO42- dimer to the F-4(7/2) of Er3+ ions. Moreover, the grain orientations due to the effect of Mo6+ ions doped in beta-TCP phosphor could play an important role in the enhancement of UC emission intensity. These results indicate that the HA/beta-TCP: Er-Yb-Mo phosphor has potential application in biological imaging and medicine. (C) 2020 Elsevier B.V. All rights reserved.