Enhancement of upconversion luminescence of YAlO3: Er3+ by Gd3+ doping

Abstract

The upconversion luminescences of YAlO3:Er 3+ phosphor co-doping with different Gd 3+ concentrations are investigated under the excitation of 980-and 532-nm diode lasers. A near ultraviolet upconversion emission at 410 nm is observed in YAlO3 under 532-nm excitation. Moreover, the inactive Gd 3+ ions can improve the upconversion intensity efficiently in a certain range of concentration. Under 980-nm excitation, the visible upconversion emissions at 546 and 646 nm are enhanced by about 10 and 8 times at the Gd 3+ concentration of 40%, respectively. The upconversion emission at 410 nm under 532-nm excitation is also enhanced by 7 times. The substitution of Gd 3+ ions for Y 3+ sites changes the local symmetry of Er 3+ , leading to the improvement of upconversion efficiency.OCIS codes: 160.5690, 160.4670, 160.4760. doi: 10.3788/COL201210.081602.In the last several decades, the upconversion luminescence of rare-earth-ion-doped materials has been investigated extensively due to their wide applications in solid-state lasers, flat panel displays, biological labeling, and so on [1−3] . Er 3+ has been reported as one of the most popular and efficient ions for upconversion [4−8] . It can provide several intermediate levels with long life time, which can be directly pumped by several diode lights [9−14] . Recently, upconversion phenomena in Er 3+ -doped YAlO 3 crystals have been widely studied because of their high mechanical hardness and considerable thermal conductivity, among others. Several authors have reported upconversion luminescence in Er 3+ -doped YAlO 3 under 518-, 542.4-, 548.9-, 652.2-, and 980-nm excitations [10,15−17] . Therefore, it is very important to improve their upconversion efficiency. There are many factors affecting the upconversion efficiency, such as the local environment, the dopant concentration, and the distribution of active ions in host materials [18] . A recent study has reported that the luminescence intensity can be enhanced by changing the local environment of luminescent centers, which can be performed by doping some suitable inactive ions in the host. , xGd 3+ (x=0, 0.15, 0.25, 0.4, 0.5, and 0.7) was prepared through a solution combustion synthesis procedure. An aqueous solution containing citric acid, Y(NO 3 ) 3 , Er(NO 3 ) 3 , and Gd(NO 3 ) 3 was used to synthesize the Er 3+ and Gd 3+ co-doped YAlO 3 powders. A citric acid-to-metal nitrate molar ratio of 1.5:1 was employed to prepare the precursor solution. After the combustion, the precursor was calcined at 1 100• C for 2 h. The powders were characterized by X-ray diffraction (XRD) on a Bruker D8 advanced equipment (x) using Cu tube with K α radiation of 0.15406 nm in the 2θ range of 20• -60• . The morphology of the prepared powders was observed by scanning electron microscopy (SEM) using JSM-6610. Upconversion luminescence spectra excited by 980-and 532-nm lasers were obtained in the spectrophotometer (R-500, Japan Spectroscopic Co., Japan). All the measurements were performed at room temperature. Figure 1 shows the representat...

Recent Trends Concerning Upconversion Nanoparticles and Near-IR Emissive Lanthanide Materials in the Context of Forensic Applications

“…Co-doping the crystalline host with other ions has been used as a strategy to improve emissive properties, [58][59][60][61] with disruption of lattice symmetry identified as a potential cause of this enhancement. [62] Manipulating the ligands contained within the host that interact with the coordination sphere of the metal is also a viable route for improved emission characteristics. Incorporation of dye molecules in one such UCNP emitter effected a 3000-fold increase in emission owing to its superior antenna effect for the Ln 3þ ion.…”