Upconversion Luminescent Properties of YVO4:Yb3+, Er3+ Nano-Powder by Sol-Gel Method

YVO4: Yb3+, Er3+ nano-sized upconversion luminescent powder was prepared by sol-gel method in the presence of citric acid. It was characterized by XRD, TEM and emission spectrum. The results show that the grain size of YVO4: Yb3+, Er3+ is under 100 nm, and its grain size and upconversion luminescent intensity all increase with roasting temperature raises. Under 980 nm laser diode (LD) excitation, two strong green emissions that centered around 523 and 551 nm were observed with naked eyes at room temperature, corresponding to the 2H11/2→4I15/2 and 4S3/2→4I15/2 transitions of Er3+, respectively. According to the dependence of green upconversion emission intensity on excitation power, it can be concluded that these two kinds of green emissions all belong to two-photon process.