Study On Synthesis And Upconversion Properties Of Yb/Er/Tm Doped TiO₂ Polycrystals

The rare earth doped upconversion luminescent material due to its multicolor adjustability and excellent fluorescence stability can be applied in many fields such as display and anti-count verfeiting.Multicolor tuning of rare earth doped polycrystalline material can be obtained via adjusting temperature and power.However,It's reported that the harsh terms to achieve multicolor output increase test conditions and costs,and limit the range of applications,including high tenperature and intense power.Therefore,emission tuning has been focused under low temperature and power.In this paper,rare earth doped TiO₂ polycrystalline materials were prepared by sol-gel method.Yb/Er doped TiO₂ polycrystalline materials?Yb/Er/TiO₂?were determined by XRD phase analysis,SEM structure analysis and upconversion spectroscopy.The best synthetic process parameters were stirring time 2 h,calcination temperature 400°C and calcination time 2 h.In these condition,Yb/Er/TiO₂ have uniform morphology and good upconversion luminescence performance.The effect of rare earth concentration and excitation power on the upconversion performance of Yb/Er/TiO₂ was investigated.The results showed that the luminescence intensities of red and green firstly increased and then decreased,with the increase of Yb/Er concentration.The supersaturation concentration caused the efficiency of energy transfer between Yb and Er to decrease.At low power from 28.6 mW to 179.5 mW,the upconversion color tuning was achieved,which moved from the pink area to the green area,and the chromaticity shift was 0.27,these result showed that Yb/Er/TiO₂ have a potential application.By using the power analysis,both red and green are two photon processes.The effects of rare earth concentration,power and temperature on the upconversion properties of Yb/Er/Tm doped TiO₂ polycrystalline materials?Yb/Er/Tm/TiO₂?were investigated.The results showed that,with the increase of Tm³⁺concentration,the intensities of red and green decreased sharply,and the intensity of blue light increased slightly.At low power from 2.0 mW to 179.5 mW,emission tunned from white to green,these result showed that Yb/Er/Tm/TiO₂ have a potential application.By using the power analysis,the red,green and blue in Yb/Er/Tm/TiO₂ are a single photon process altogether.Via adjusting the temperature from 313 K to 563 K,Yb/Er/Tm/TiO₂ upconversion color shift was realized,which moved from glaucous to yellowish green.The temperature sensitivity of Er³⁺thermal coupling energy level was explored,the temperature sensitivity coefficient is 2177/T²;the temperature coefficient of non-thermal coupling energy level(⁴F_9/2/2 energy level of Er³⁺and ³F₄ energy level of Tm³⁺)is 2836/T²,both the temperature sensitivity coefficient was higher than other oxide systems,and Yb/Er/Tm/TiO₂ had a excellent application prospect in the field of temperature detection.