A novel upconversion emission material based on Er3+ - Yb3+ - Mo6+ tridoped Hydroxyapatite/Tricalcium phosphate (HA/β-TCP)

Abstract In this paper, a novel material based on Er-Yb-Mo tri-doped HA/β-TCP phosphor for intense green up-conversion (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 β-TCP phase has a rhombohedral structure, which is controlled by the doped ions. Under excitation wavelength of 976 nm laser diode, the HA/β-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 (2H11/2, 4S3/2) - 4I15/2, 4F9/2 - 4I15/2 transition of the Er3+ ion, respectively. Remarkably, compared with the sample without Mo6+, the green emission intensities increased ∼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 |2F7/2, 3T2> state of Yb3+ - MoO42− dimer to the 4F7/2 of Er3+ ions. Moreover, the grain orientations due to the effect of Mo6+ ions doped in β-TCP phosphor could play an important role in the enhancement of UC emission intensity. These results indicate that the HA/β-TCP: Er-Yb-Mo phosphor has potential application in biological imaging and medicine.