Study On The Upconversion Luminescence Of Rare-earth Doped NaNbO₃ And Sr₂TiSi₂O₈

Rare-earth (RE)-doped upconversion luminescence materials for conversion of efficient infrared into visible or ultraviolet light are very attractive for modern technology. These materials have a variety of potential applications in several areas, such as color displays, sensors, detection of infrared radiation, and upconversion lasers. Perovskite alkaline-earth stannate are extensively investigated due to their unusual dielectric and semiconducting properties, and extensive application in gas or humidity sensors, lithium ion batteries, thermally stable capacitors, and photocatalytic utilization. Perovskite alkaline niobates represent a particularly interesting class of materials that exhibit various properties, such as ferroelectric, piezoelectric, ionic conductive, photorefractive and photocatalytic properties. Except for above of all the priority,nanocrystal NaNbO₃ dominates a low maximum phonon energy and easy fabrication.It is the best host material.In this paper NaNbO₃ samples were prepared by hydrothermal , before NaNbO₃ , NaNbO₃:Er³⁺and NaNbO₃:Sm³⁺ samples were prepared by solid state reaction method. It is seen that these three nanocrystals can give the green emission and red emission, which are attributed to the intra-4f transition of 4H11/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 of Er³⁺ ions, respectively. The XRD experiment revealed that NaNbO₃ (hydrothermal 200oC and annealing temperature 900 oC by solid state), NaNbO₃:Er³⁺(annealing temperature 900 oC ),NaNbO₃:Sm³⁺(annealing temperature 900 oC)had cubic structure while at annealing temperature 800,950and1000 oC had orthogonal crystal structure. Under 980nm LD excitation, the up-conversion emissions at 526, 547 and 662 nm (Er³⁺), 526, 550 and 660nm (Sm³⁺) were recorded. The luminescent procedure of Er³⁺ and Sm³⁺ were discussed. The effect of annealing temperature and symmetric on luminescent properties of NaNbO₃:Er³⁺samples were studied. The results show that Up-conversion emission intensities of NaNbO₃: Er³⁺samples increases with increasing annealingtemperature and decreasing symmetric.in addition, Er³⁺doped and Er³⁺/Yb³⁺co-doped Sr₂TiSi₂O₈ samples were synthesized by solid-state reaction. The intensities of up-conversion luminescence as a function of the rare-earth ions concentration were investigated. And excited state absorption and energy transfer process were also discussed as the mechanisms for the visible emissions.