Preparation And Properties Of Fluorophosphate Radiation-resistant Optical Glass

The design and development of new type of radiation resistant optical glass,and further revealing the change and mechanism of microdefects induced optical absorption characteristic against high energy ion irradiation through irradiation experiments,to achieve breakthrough in the glass formulation development and preparation technology of high performance and high quality space radiation resistant optical glasses,together with the improved technical ability of active antiradiation strengthening measures for space optical system based on use of radiation resistant optical glasses as their key components,will support the innovative design and development of space long-life radiation resistant optical loads.It is of great application value to China's major Aerospace Science and technology projects.In this paper,based on the design theory of glass composition-network structure of fluorophosphate glasses,the fluorophosphate radiation resistant glasses is designed and prepared with the basic glass compositions of(45-50)Ba(PO3)2-(15-20)AlF3-(0.5-2)BaF2-(3-5)MgF2-(0-1.5)-ZnF2-(0-1.5)LiF.Through systematic experiments and analysis of the glass properties before and after ? irradiation,such as the change of transmittance and optical density increment,the change of glass structure,the generation and evolution of microdefects,etc.,the effects of glass melting atmospheres,the doping content of CeO2,and the co-doping of Sb2O3 and Bi2O3 on the optical transmittance and radiation resistance of the prepared fluorophosphate glasses are studied.The mechanism of diversity in the radiation resistance of the materials is clarified from the change of the glass microstructure and the absorptive defects,so as to optimize the composition and the preparation process of the fluorophosphate glass and realize the effective regulation of their radiation resistance.The results of this paper can provide theoretical and technical support for the research and development of new fluorophosphate irradiation resistant optical glasses with low refractive index and low dispersion and their engineering applications.The main research results are as follows:(1)The influence of CeO2 content on the optical properties of fluorophosphate glass and the inducible causes for the microscopic defects formation under high-energy irradiation:With the addition of CeO2,the UV absorption cutoff edge redshifted due to the absorption of Ce4+ions at 4.3 eV.Addition of 0.34wt%CeO2 enhanced the connectivity of the main phosphate-chain in the fluorophosphate glass structure and reduced the proportion of non-bridged oxygens,but larger doping content of CeO2 more than 0.6wt%increased the proportion of non-bridged oxygens.After y ray irradiation,more microdefects of POHC,PO2-EC,PO3-EC and PO4-EC were produced in the base glass,resulting in a sharp decrease in the visible transmittance.Compared with the base glass,the CeO2 doped fluorophosphate glasses showed significant decrease in both the transmittance and the optical density increment.When the CeO2 content in the fluorophosphate glass increases gradually from 0 to 0.34wt%,0.6wt%and 0.9wt%,the optical density increment of the corresponding samples at 385nm wavelength decreased from 0.4336 to 0.2312,0.1911 and 0.1744,respectively after the total dose of 250krad(Si)irradiation,indicating the gradual improvement in radiation resistance of the fluorophosphate glasses,which is witnessed by the decrease of the irradiation-induced defects proportion of PO3-EC,PO4-EC,POHC and OHC.Considering both the UV transmittance and optical density increment of the glasses,0.34wt%CeO2 is the appropriate dosage of radiation stabilizer for the fluorophosphate glass with radiation resistance capacity of 250 krad(Si).(2)The effect of glass melting atmospheres on the optical properties and microdefects of the fluorophosphate glasses and the evolution mechanism of irradiation-induced defects:Cerium ions usually coexists in glass with both Ce3+ and Ce4+ states,and the ratios of Ce4+/(Ce3++Ce4+)in the as-produced FP:Ce(O2),FP:Ce(air),FP:Ce(N2)glasses were adjusted through various melting atmospheres,which was 77.49%,92.49%and 56.5%,respectively.Fe3+ ratio is the highest under O2 atmosphere,which resulted in the largest red-shift of UV absorption edge.And the higher ratio of Ce4+/(Ce3++Ce4+)reduced the proportion of irradiation-induced PO3-EC and PO4-EC defects in the FP:Ce(O2)glass by trapping the holes through Ce4+.The sample prepared in N2 atmosphere had highest Ce3+proportion,which reduced the irradiation-induced OHC and POHC defects by trapping the holes,but the lower proportion of Ce4+/(Ce3++Ce4+)cannot effectively suppress the formation of PO3-EC and PO4-EC defects.Moreover,the melting of fluorophosphate glass in O2 and N2 atmospheres increased the nonbridging oxygen content in the produced glasses,which is not conducive to improve their radiation resistance.The ratio of Ce4+/(Ce3++Ce4+)in the fluorophosphate glass melted in air is the highest,which can suppress the electron-related PO3-EC and PO4-EC defects,and effectively improved the radiation resistance of the FP:Ce(air)glass.The transmittance at 385nm decreased for these CeO2 doped fluorophosphate glasses and their optical density the increments were 0.1768,0.2191,and 0.2428 for the FP:Ce(air),FP:Ce(02),FP:Ce(N2)samples when the cumulative total dose of radiation reached 250 krad(Si).To melt the glass in air helped to control the existence of Ce ion in terms of Ce4+in the FP:Ce(air)glass,which inhibited the electron-related PO3-EC and PO4-EC defects,resulting in the minimized optical density increment at 385 nm,and therefore the relatively optimal radiation resistance.(3)Effects of co-doping of Sb2O3,Bi2O3 with CeO2 on optical properties and irradiance resistance of the fluorophosphate glasses:The introduction of Sb2O3 and Bi2O3 slightly lowered the overall thermal stability of CeO2-doped fluorophosphate glasses.Doping of Sb2O3 and Bi2O3 caused the red-shift of UV absorption edge,i.e.the UV absorption cut-off wavelengths of CeO2 single-doped(FP:Ce)and co-doped(FP:Ce,Sb,FP:Ce,Bi and FP:Ce,Sb,Bi)samples are 361nm,366.9 nm,374.2 nm and 387.3 nm,respectively.Under different irradiation doses of 10,100 and 250 krad(Si),the optical density increment of fluorophosphate glasses at 385nm increases in the order of FP:Ce,Bi<FP:Ce,Sb,Bi<FP:Ce and Sb<FP:Ce<FP.In the case of 250 krad(Si)total dose irradiation,the optical density increments of the above corresponding samples are 0.1482,0.1818,0.2624,0.2857 and 0.4486,respectively.Non-bridging oxygen is the precursor of various irradiation-induced defects in the fluorophosphate glasses.Doping of Sb2O3 significantly increased the ratio of non-bridging oxygens and the corresponding FP:Ce,Sb sample have the highest proportion of irradiation-induced OHC,PO4-EC and PO3-EC defects and thus worser radiation resistance.Doping of Bi2O3 can significantly reduce the proportion of non-bridging oxygens,which leads to the smallest proportion of OHC and POHC,PO3-EC,PO4-EC defects in corresponding FP:Ce,Bi sample and therefore best radiation resistance.On the basis of doping CeO2,addition of Bi2O3 improved the radiation resistance of fluorophosphate glass more effectively than introduction of Sb2O3.Simultaneous introduction of Sb2O3 and Bi2O3 is not as good as introducing Bi2O3 alone to work together with doped CeO2.