The Application Of Positron Annihilation Technology In Characterization Of Glass Properties And Structures

In this work, the positron annihilation lifetime spectra were used to characterize properties and structures of oxide glasses, chalcogenide glasses and porous glasses. The main contents of study include relationship between glass compositions and structure, crystallization processes, irradiation induced effects as well as micro-structures on glasses. At the same time, conventional measurements, such as density, microhardness, the absorption spectra and transmittance spectra and XRD were used as an assistant to compare with the results of positron annihilation lifetime spectra. The results showed that the positron annihilation lifetime spectra were an excellent probe for the study of the glass compositions, crystallization properties, porosity of porous glasses and anti-irradiation properties of glasses, especially, for the nano-sized defects existing in the glass network structures. Studied glass compositions include ZnO-based scintillating glasses (55-x)SiO2-45ZnO-xBaF2 (x=5,10,15), heavy metal oxide glasses xPbO-10B2O3-(90-x)SiO2 (x=40,45,50,55) and chalcogenide glasses GeS2-Sb2S3-PbS and (80-x)GeSe2-xAs2Se3-10PbSe (x-10-90). The measured positron annihilation lifetime spectra showed that variation of positron lifetime parameters matched well with the results of measured glass density, micro-hardness, the absorption spectra and transmittance spectra and XRD spectra. The positron lifetime spectra of oxide glasses and chalcogenide glasses under different thermal treatment conditions also showed good consistency with the trend of glass absorption spectra and transmittance spectra. The studies of sulfide glasses exhibited the transmittance spectra with the variation of short wavelength absorption edges indicating formation of nanosized crystal in the glasses after thermal treatment. However, conventional XRD spectra are not sensitive enough to probe this process while the positron annihilation lifetime spectra can do. The positron annihilation lifetime spectra were used to study the anti-irradiation properties of heavy metal oxide glasses55PbO-10B2O3-35SiO2 and 50Bi2O3-10B2O3-32SiO2-8Sb2O3 under different irradiated doses which matched well with the transmittance spectra of the glasses. Especially, for50Bi2O3-10B2O3-(40-x)SiO2-xSb2O3 (x=0,1,3,8)glasses, after irradiated under 15.5kGy dose, all Sb2O3-containing samples had longerτ1 andτ2 than Sb2O3-free sample, which matched exactly with the trend of UV-Vis spectra.This work also studied the porosity properties of porous glasses by the longest positron lifetimeτ3 and its intensity I3. Base on the principle of the positron annihilation, the longest lifetimeτ3 can be used to represent the size of porosity and its intensity can be used to represent the density of porosity in porous glasses. The effects of the type of acid, the concentration of acid, the treatment time of acid, the treatment temperature of acid and the ratio of acid to glasses during the acid leaching of porous glasses were studied by using DOE method. From DOE analysis, among this five factors, the ratio of acid to glasses and the type of acid exerted major effects on theτ3 while the ratio of acid to glasses and the concentration of acid were the key factors to the I3.