The Synthesis And Properties Of Red And Near Infrared Persistent Luminescence Materials

Long persistent luminescent materials have a wide range of applications in areas such as low-light illumination and decorative indicators due to their unique optical properties.Currently,blue and green persistent luminescent materials have excellent performance,but red and near-infrared persistent luminescent materials have poor performance.In view of the lack of red and near-infrared long-wavelength persistent luminescent materials and the incomplete of the persistent luminescent mechanism,we have designed and synthesized three novel long-wavelength persistent luminescent materials and systematically studied their luminescence and persistent luminescence properties.The specific research content and main results of this paper are as follows:A novel germanate persistent luminescent material CaMgGe₂O₆:Mn²⁺was successfully synthesized by high-temperature solid-state reaction,and an empirical energy level diagram of CaMgGe₂O₆:Ln²⁺/Ln³⁺was established based on the Dorenbos model.Theoretically predicting the best co-doped rare earth ions of the CaMgGe₂O₆:Mn²⁺phosphor.After doping with Sm³⁺,the initial brightness of the persistent luminescence was increased by 16 times and the duration of the persistent luminescence was increased by 52 times.The persistent luminescent duration of the sample was nearly 60 minutes above the recognizable brightness level（≥0.32mcd/m²）.We also compared our sample with the red commercial persistent luminescent material Y₂O₂S:Eu³⁺.According to the analysis of thermoluminescence curve,it is known that the improvement of the persistent luminescent property is caused by the doping of Sm³⁺.A possible persistent luminescent mechanism is proposed based on the experimental data,and explaining the persistent luminescence process,namely Donrebos electron capture afterglow mechanism model.A novel germanate persistent luminescent material SrMgGe₂O₆:Mn²⁺,Sm³⁺was successfully synthesized by high-temperature solid-state reaction.The crystal structure,luminescent properties,band gap and band structure of the material were systematically studied.SrMgGe₂O₆:Mn²⁺,Sm³⁺shows red and near-infrared long persistent luminescence with 666nm emission peak after 10 minutes UV light excitation.The persistent luminescence duration lasts about 45 minutes above the recognizable brightness level（≥0.32mcd/m²）.The analysis of the thermoluminescence curve shows that the persistent luminescence property of the sample is mainly due to the doping of Sm³⁺create a new position trap and sensitize a original position trap.In addition,we propose a possible persistent luminescent mechanism based on the experimental data and explain the entire process of persistent luminescence.The garnet long persistent luminescent materials Na₂CaSn₂Ge₃O₁₂:Pr³⁺and Na₂CaSn₂Ge₃O₁₂:Cr³⁺were successfully synthesized by high-temperature solid-state reaction.The crystal structure,luminescent properties and persistent luminescent properties of these two materials are studied.The Na₂CaSn₂Ge₃O₁₂:Pr³⁺sample exhibited a red emission of 612 nm,and its persistent luminescent duration was above the recognizable brightness level（≥0.32mcd/m²）for about 60 minutes.According to the analysis of thermoluminescence curve,it can be known that the reason of the persistent luminescence phenomenon is a trap at the position of 0.69eV below the conduction band in Na₂CaSn₂Ge₃O₁₂:Pr³⁺sample.The trap at this position will capture electrons and slowly release them,resulting in a better persistent luminescenct phenomenon.The photoluminescence and persistent luminescence of the Na₂CaSn₂Ge₃O₁₂:Cr³⁺sample is a broadband emission peak centered at 802nm,and the luminescenct color is not visible to the naked eye.With a special near-infrared imaging system,the persistent luminescence of the sample can be observed for about60min.