Luminescent Properties Of Cu Ions In Several Aluminates(CaAl₂O₄,CaAl₄O₇,Sr₄Al₁₄O₂₅),Gallate(BaGa₂O₄) And Silicate(SrSiO₃) Phosphors

Among current functional luminescent materials,lanthanide ions such as Eu²⁺,Tb³⁺and Ce³⁺,play a dominate role wheter as emission centers or carrier trapping centers.However,the relevant environmental pollution and difficulty in separation is becoming a spiking issue,which seriously affects the further industrial development of lanthanide-ion-doped luminescent materials.As a contrast,transition metal ions with the raw materials widely available have a large spectrum of energy levels.Their spectra can be adjusted among different crystal environments.But,apart from present Mn⁴⁺and Cr³⁺activated commercial phosphors,other transition-metal-ion doped functional materials are still scare.Moreover,Mn⁴⁺and Cr³⁺activated materials normally give the emission in near infrared region(longer than 650 nm),which is less sensitive for human naked eyes.Therefor,there is still a long way to go to develop highly efficient transition-metal-ion doped luminescent materials,especially with the emission at about 600 nm.In the past decades,it was observed Cu²⁺and Cu⁺could exhibit their peculiar adjustable emission in a variety of compounds.But their luminescence behavior and the underlying luminescence mechanisms are still unclear,which in a large margin seriously hinders the developments of prevelent Cu-ion-doped functional materials and further lanthanide-replacement works.This paper,as examples,focused on several Cu ion-doped aluminates(CaAl₂O₄,CaAl₄O₇,Sr₄Al₁₄O₂₅),gallate(BaGa₂O₄)and silicate(SrSiO₃),to tentatively investigate their luminescent properties and their luminescent mechanisms.The relationships between the Cu luminescent properties and the relavent host electronic structure,the lattice environment are roughly established.The main research contents are as follows:1.The luminescent properties of copper ions in aluminates(CaAl₂O₄,CaAl₄O₇,Sr₄Al₁₄O₂₅)materials were investigated.The results showed that the emission wavelength of Cu²⁺had a stong dependence on its occupied crystal coordination environment.In addition,its emission wavelength had a linear relationship with the energy difference between the groud state of Cu⁺and the top of the valence bands of the host.2.Based on the above research results,we tentatively designed a new Cu-doped long afterglow material BaGa₂O₄:Cu and investiged its luminescent behavior.The results showed that,Cu²⁺ions could achieve a broadband emission with a main peak at 570 nm under excitation of 350 nm,which was attributed to the CT transition of Cu²⁺.Whereas,it also could give an emission at 563 nm under the excitation of 286 nm,which could be attributed to the 4s?3d transition of Cu⁺.Interestingly,it could give an extreme long afterglow with a decay longer even than 14 h with a rare-reported golden-ligh after ceasing the exposition to the ultraviolet light.3.The luminescence behavior of copper doped SrSiO₃ was preliminarily explored.The results showed that Cu²⁺,as the interstitial ion among the tetrahedra SiO₄,could produce both emission at 466 and 518 nm,which could be attributed to the charge transfer band of Cu²⁺.By comparing the crystal structure and luminescence properties of Sr_1-xCu_xSiO₃and Ca_1-xCu_xSiO₃,it could be concluded that the emission wavelength of Cu²⁺would blue-shift with the increase of the host structural parameters.