Study On Optical Properties Of Rare Earth Doped Tungsten/Molybdenum Ore

China is a tungsten/molybdenum mine resources country in the world,with abundant tungsten/molybdenum deposit widely distributed.It is worth mentioning that the reserves and output of tungsten/molybdenum ore resources in Henan Province are among the best in China.These unique resource advantages have laid the foundation for the study of tungsten/molybdenum ore materials.In addition,increasing the added value of tungsten/molybdenum ore material is very important to improve its industrial economic benefits.Rare earth is known as“industrial monosodium glutamate”.Rare earth ions have rich electron level structure,and their doping in specific matrix materials can realize the emission of various bands from ultraviolet light,visible light to infrared light,which is a veritable“luminous treasure house”.The luminescence properties of rare earth depend heavily on the matrix materials,and tungsten/molybdenum materials have unique crystal structure,which provides conditions for the study of special optical properties of rare earth.The purpose of this paper is to realize the unique luminescent properties of the material by doping rare earth in tungsten/molybdenum ore,and to improve the added value of tungsten/molybdenum ore products by further exploring its application value.It is found that the rare earth doped tungsten/molybdenum ore have some optical phenomena which are different from the conventional luminescent materials.The special phenomena are used to realize the application of this kind of material in fluorescence security,information encryption and temperature detection successfully.The content and results of this paper are as follows:（1）A unique intelligent upconversion material Y₂Mo₄O₁₅:Yb³⁺,Ho³⁺has been prepared by high-temperature solid-state sintering method,which can respond to the power density or pulse width of 980 nm excitation light.The upconversion luminescence color of the material can be changed from red to yellow and then from yellow to green when the power density of the excitation light increases from 0.5 to 100 W/cm².In addition,its upconversion luminescence color can also be tuned from red to yellow and then to green when the pulse width of the excitation light reduces from 10 to 0.1 ms.We found through fluorescence lifetime and steady-state spectroscopy that electrons at the ⁵I₆ energy level have two competing processes.Due to the high phonon energy(1039 cm^-1)of the matrix material,the transition path of the excited electrons is altered,resulting in a special upconversion luminescence.Finally,we designed a unique chameleon-like rare-earth doped molybdenum upconversion luminescent material with excitation power density dependent and pulse width dependent optical properties,and developed its applications in the field of fluorescence anti-counterfeiting and information encryption by using these two properties.The development of such intelligent upconversion materials with novel optical properties is of great significance to the fields of anti-counterfeiting and information encryption,which has been the research frontier and hot spot in this field.（2）A transition metal/rare earth co-doped tungsten ore proportional luminescent thermometer excited by blue LED was prepared.Al₂W₃O₁₂:Cr³⁺,Eu³⁺with two distinct dual-emission centers was also synthesized by high-temperature solid-state sintering method,in which both Cr³⁺and Eu³⁺ions could be effectively excited by commercial blue LED.In addition,when transition metal ions are co-doped with rare earth ions in the matrix material,energy transfer（ET）often occurs between the two doping ions.However,for Al₂W₃O₁₂:Cr³⁺,Eu³⁺,spectra and fluorescence lifetime indicate that there is no ET between Cr³⁺and Eu³⁺ions.It is worth noting that the photothermal stability of Eu³⁺ions is much better than that of Cr³⁺ions through the variable temperature spectrum,and the I_Cr/I_Eu decreases linearly with the increase of temperature.For this purpose,we propose a blue-LED-excitable self-calibrating luminescent thermometer（SCLT）based on Cr³⁺/Eu³⁺co-doped Al₂W₃O₁₂.Compared with existing transition metal/rare earth-based luminescence thermometers,the developed SCLT has high absolute sensitivity(0.38 K^-1),relative sensitivity(2.9%K^-1)and good cycle stability.