Crystal Structure And Spectral Tuning Of Silicate (Germanate) Luminescent Materials

Rare earth doped silicate luminescent materials have the advantages of high thermal stability,high chemical stability and high quantum efficiency,etc.With excellent performance,this kind of luminescent materials is widely used today.Since germanium and silicon are in the same main group,the crystal structures of germanate are very similar to that of silicate.Based on this,it's reasonable to expect that germanate is also a promising type of luminescent material with great development prospects.The purpose of this research is to discover new rare earth doped silicate?germanate?luminescent materials and to explore the relationship between crystal structures of host or lattice sites of the rare earth ions and the luminescent properties.The Eu²⁺doped Sr_1-xBa_xAl₂Si₂O₈ luminescent material was studied.In the solid solubility range of 0<x<0.75,the crystal form of Sr_1-xBa_xAl₂Si₂O₈:Eu²⁺luminescent material remains the same,but the unit cell parameters show a linear rise with the increase in substitution amount?x?.At the same time,the emission spectrum of the luminescent material undergoes a red shift from 415 nm to 450 nm due to a larger crystal field splitting effect caused by the decrease in the distance between Eu²⁺and the coordination O^2-ions.Studies have shown that by substituting Ba²⁺for Sr²⁺ions,the crystal structure of Sr_1-xBa_x Al₂Si₂O₈:Eu²⁺can be tailored,and the purpose of spectral controllable tuning can be achieved.The Eu²⁺/Eu³⁺co-doped Sr_1-xBa_xAl₂Si₂O₈ luminescent material was studied.With the increase in Ba²⁺ion content,the unit cell parameters showed a linear increase.Corresponding to this,the emission of Eu²⁺gradually weakened and the emission of Eu³⁺gradually enhanced.Further research shows that this is due to the introduction of lattice stress by ion substitution,and the generation of stress inhibits the reduction of Eu³⁺.This study shows that control of Eu element valence state and the controllable tuning of the emission spectrum can be achieved by the simple cation lattice design method.The crystal structure and luminescent properties of Ce³⁺doped Sr₃MgSi₂O₈ luminescent materials were studied.This luminescent material undergoes concentration quenching by means of dipole-dipole interaction between Ce³⁺ions.The luminescent material has excellent thermal stability.When the temperature reaches 150°C,the emission intensity remains 90%of that at room temperature.The relative position of Ce³⁺ion level between the valence band and conduction band of the host was determined.Through further discussion,the thermal quenching mechanism of the luminescent material was determined to be thermal ionization.The relationship between ion occupation sites and emission spectrum of Ce³⁺-doped Ca₃Sc₂Ge₃O₁₂2 luminescent material was studied.It is observed that Ce³⁺ions show two luminescent centers in a single lattice site.Through site-selective and time-resolved spectroscopy,the excitation positions of the two emission centers were 425 nm and 450 nm,and the emission positions were 490 nm and 530 nm,respectively.The mechanism of this phenomenon is thought to be the generation of Ce³⁺ion pairs.The luminescent material has excellent thermal stability.When the temperature reaches 150°C,the emission intensity remains 90%of that at room temperature.