Preparation And Characterization Of Er³⁺/Yb³⁺ Co-doped With NaGdF₄ Luminescent Materials

Rare earth luminescent materials have characteristics such as low radiation damage,high chemical stability,weak autofluorescence,and strong absorption capacity,making their research value in the field of rare earth functional materials rank in the forefront.NaGdF₄ has attracted wide attention due to its excellent photo-magnetic properties,low phonon energy,high up-conversion efficiency,and wide UV-infrared optical transmittance.In this paper,the NaGdF₄:Er³⁺/Yb³⁺nano-upconversion luminescent material is studied from the perspectives of crystal structure,luminescence regulation and mechanism analysis by combining first-principles calculations with experimental preparations,and focuses on its luminescence performance under dual-wavelength excitation.The structural properties,electronic properties and optical properties of undopedβ-NaGdF₄ system,Er³⁺dopedβ-NaGdF₄ system and Er³⁺/Yb³⁺co-dopedβ-NaGdF₄ system are calculated by Materials Studio software.The results show that Er³⁺doping and Er³⁺/Yb³⁺doping did not destroy the original hexagonal phase structure,and the volume was slightly reduced,the forbidden band width was greatly reduced,which was conducive to the transition of electron.After doping the Er³⁺and Er³⁺/Yb³⁺,the absorption rate of the system in the infrared band is increased,and the reflectivity decreases,which is more propitious to the realization of up-conversion luminescence.The NaGdF₄:Er³⁺/Yb³⁺nano-upconversion phosphor is synthesized by hydro-thermal method,and the crystal structure and morphology are controlled by changing the reaction conditions.Hexagonal phase nanoparticles with good crystallinity and uniform size around 36 nm can be obtained under the optimal preparation conditions.When excited separately at 980 nm or 1550 nm,the doped system all produced green light emission peaks at 523 nm and 542 nm and red light emission peaks at 656 nm.The dual-wavelength synergy produced when dual wavelength（980 nm and 1550 nm）co-excite NaGdF₄:Er³⁺/Yb³⁺nanocrystals can make the emission center have a larger absorption cross-section,more emission paths,and less non-radiative relaxation.There by greatly improving the utilization rate of absorbed photons,realizing the improvement of the luminous intensity of the sample and the adjustment of the fluorescent color.An up-conversion logic gate is constructed based on the special up-conversion luminescence characteristics of dual-wavelength excitation,which used the wavelength excitation condition as input signal,and the relative fluorescence intensity of red and green light,red-green ratio and green-red ratio as the output signal.Hope to provide useful ideas for the application of rare earth nano-luminescent materials in the field of logic.