Intense green upconversion emission of rare-earth-doped Sr3(PO4)2/Sr2P2O7 powder: Effect of annealing temperature and temperature-sensor properties

A series of Mo6+-doped Sr-3(PO4)(2)/Sr2P2O7: Er3+-Yb3+ was synthesized by coprecipitation followed by heat treatment. X-ray diffraction and scanning electron microscopy analyses confirmed that the annealing temperature strongly influenced the morphology and structure of the material. Under laser-diode excitation wavelength of 975 nm, the green and red upconversion emission intensity as a function of annealing temperature reached its maximum value at 1000 degrees C. The green emission intensity of the 3 mol% Mo6+-doped sample sharply increased, becoming about similar to 143 times higher than that of the undoped samples. Furthermore, the obtained phosphor presented a high temperature sensitivity of S-a and S-r with a maximum value of 1.05% K-1 at 363K and 0.8% K-1 at 303K, respectively. These results indicated that the Sr-3(PO4)(2)/Sr2P2O7: Er-Yb-Mo phosphor was an efficient upconversion luminescent material suitable for thermal-sensor applications. The selection and control of annealing temperature played a key role in the success of the synthesis and acquisition of the phosphor's desired physical property. Finally, several explorations in this work that enhanced UC luminescence by using the transition-metal ion Mo6+ provided a novel idea to design strong UC emission biomaterials for their medical applications.