Study On The Mechanism And Some Of Applications In BaFX: Eu²⁺(X=Cl, Br)

For the sake of better understanding to the optical properties of electron trapping materials and further improvement of their optical storage capability,the formation of electron/hole traps and trapping mechanism in BaFX:Eu²⁺(X=Cl,Br) were mainly investigated.Investigations were also made to further improve the spatial resolution of storage screen and decrease the depth of electron traps to match common laser.The optical absorption spectra were intensively studied to investigate the energy transfer processes and possible trap centers in BaFX:Eu²⁺(X=Cl,Br).These results suggest that(1) in the write-in process,the electron transfer is mainly via tunneling,and in the readout process,the electrons in F(F^-) and F_a centres are more likely via tunneling, and that in F(Cl^-) centres,more likely via conduction band;and(2) there exist some hole traps in BaFCl:Eu²⁺ phosphor.When they trap holes,the corresponding absorption bands present around 270,315 and 378nm respectively.They are tentatively attributed to H(F₂^-) centers,O_F^- centers and hole trap centers related to Cl^- ions,which presented the spectroscopic identification for the possible hole traps contributing to the photostimulated luminescence(PSL).However,screen made from powdered phosphors suffers from inferior spatial resolution due to light scattering of the readout laser beam by crystal grains. BaFX:Eu²⁺(X=Cl,Br) embedded oxide glass ceramics were prepared,which show similar photoluminescence(PL) and PSL properties as powdered sample.Besides, BaFBr:Eu²⁺ nanoparticles were also synthesized by microemusion systems.Theses results were interesting since spatial resolution could be improved by this means.In addition,optical storage were observed in Eu²⁺ doped MBrCl(M=Sr,Ba) and Ce³⁺ doped BaBrCl.BaBrCl:Eu²⁺ shows an emission band peaked at 413nm,and two difference absorption spectra(DAS) bands peaked at～550nm and 675nm respectively. The stimulation energy is lower than that of BaFX:Eu²⁺(X=Cl,Br),and matches the cheaper,more portable and more convenient semiconductor laser better.