Study On Glass Formation Ability, Crystallization Control And Location Of Rare Earth Ions In Chalcogenide Glass

Rare-earth doped chalcogenide glass-ceramic is regarded as an important Mid-infrared optical material.However,two challenging issues still need to be addressed for the practical application of the materials.They are:（1）uncontrollable crystallization in the process of ceramic treatment;（2）ambiguous chemical environment of rare earth ions in the glass-ceramics.To solve these,we develop an innovative approach to use the non-stoichiometric rare earth doped chalcogenide glass matrix as the starting materials.By changing the glass compositions and the ceramic processing parameters,we would explore how to control the crystallisation effectively in the process of ceramic treatment,and demonstrate how to identify the local chemical environment of the rare earth ions in the glass-ceramics.This will develop a method to tune the crystallisation perfectly in the process of ceramic treatment,and precisely identify the chemical environment of rare earth ions in the glass-ceramics.We have done related research.The main conclusions are as follows:（1）The ternary Ge_XGa₄S_96-X（x=22.5,27,30,33,36）chalcogenide glasses were prepared（composition ranging from S-rich to stoichiometric,to S-poor）.High-resolution X-ray photoelectron spectroscopy was used to detect the structural evolution of Ge-Ga-S glass,and the presence of microscopically ordered structures in the ternary chalcogenide glass was detected.It was,thus,confirmed that the ternary Ge_XGa₄S_96-X6-X chalcogenide glass has a good glass forming ability.（2）The prepared Ge-Ga-S glasses（the glass composition designed from S-rich to stoichiometric,and then to S-poor,the content of Ge increasing with decrease of that of S）were annealed in the condition that the annealing temperatures were 20℃higher than their respective glass transition temperature.X-ray diffraction and Raman scattering spectra were used to characterize the structures.It was found that after annealing for a long time GeS₂ and GeS crystals can only be precipitated in non-stoichiometric component glass ceramics with S-rich and S-poor,respectively,and the crystals are uniformly distributed;After annealing for a short time,the GeS,Ga₂S₃ and GeS₂ crystals appeared simultaneously in the stoichiometric glass ceramic.It has been confirmed that some properties of the optical glass in the instrument can be regulated by designing the glass composition.（3）Had been annealed for 30 hours,Ge₂₅Ga₁₀Se₆₅+0.5wt.%Er chalcogenide glass was subjected to linear EDS scanning in STEM mode by TEM,and then the EDS linear scan results were mapped to fit the distribution of the doped rare earth ions.It was found that most rare earth ions were distributed near the Ga₂Se₃ nanocrystals indicating the formation of Ga-REI or Ga-Se-REI bonds on the surface of precipitated crystals to prevent photoluminescence quenching caused by rare earth ion clusters.