Oxygen vacancy substitution tuning photoluminescence of self-activated LiGaSi(1-)Ge O4 phosphors

Preparing low-cost and multifunctional phosphor is an important and challenging job. In this paper, a high-purity self-activated LiGaSiO4 phosphor has been successfully synthesized by the high-temperature solid-state method, which can emit near-infrared light peaking at 697 nm. The reversible thermochromic phenomenon can be observed by heat-treating LiGaSiO4 compounds in different atmospheres. The luminescent mechanism and thermochromic phenomenon are studied in detail by photoluminescence spectrum, electron paramagnetic resonance and the first principle calculations. The results show that oxygen vacancies in LiGaSiO4 compounds play an important role in the near-infrared luminescence process. Based on this luminescent mechanism, a series of LiGaSi(1-x)GexO4 (x = 0.2, 0.4, 0.6, 0.8, 1.0) self-activated phosphors have been fabricated and the corresponding luminescent modulation has been inferred. The results indicate that thermochromic LiGaSi(1-x)GexO4 phosphors can be used as special anti-counterfeiting and bio-imaging materials.