Investigation on Photoluminescence and Mechanoluminescence of Single Tb3+-doped Intense Green Phosphor

Mechanoluminescent (ML) materials can directly convert mechanical energy into optical energy and play a significant role in stress monitoring, anti-counterfeiting, etc. However, most of green ML materials need to be synthesized under high temperature and reducing atmosphere, which makes the development of green ML materials urgent. Rare earth ion Tb3+ is regarded as one of the most potential activators in green phosphor materials. In this work, novel single Tb3+-doped ss-KMg(PO3)(3) green phosphors were synthesized via high temperature solid state method. The structure was characterized via X-ray diffraction (XRD) and scanning electron microscope (SEM). The photoluminescent (PL) properties were studied by excitation and emission spectra. It shows strong f-f transition excitation peaks in the UV region with a high quantum yield of 90.74%. The color coordinate of ss-KMg(PO3)(3):Tb3+ is close to that of commercial green phosphor, resulting from the D-5(4)-F-7(J) (J=6, 5, 4, 3) transition emission of Tb3+. Tb3+ occupies Mg2+ sites, and the defects caused by charge difference are verified by thermoluminescence (TL). The existence of multiple trap levels makes the phosphors possess excellent thermal stability. More importantly, ss-KMg(PO3)(3):Tb3+ exhibits outstanding ML properties. The trap levels formed by the defects play a significant role in the process of ML. Under the stimulation of mechanical stress, the electrons and holes in the trap levels are released to the excited states and ground states of Tb3+ respectively, and the D-5(3)-(7)FJ (J=6, 5, 4) and D-5(4)-F-7(J) (J=6, 5, 4, 3) transitions of Tb3+ are realized. Both the powders and the polydimethylsiloxane (PDMS) composite materials show excellent PL and ML properties. The high sensitivity to stress is attributed to the flexible structural framework of ss-KMg(PO3)(3), which is easy to generate high strain energy. The materials have promising application prospect in solid state lighting, display and stress sensing.