Controllability Of Crystallization And Physicochemical Properties Of GeS₂-based Chalcogenide Glass-ceramics

This dissertation reports the results on the crystallization mechanism, controllable preparation and properties of GeS2 and its quasi-binary or ternary chalcogenide glass-ceramics. Based on the understanding of controllability of crystallization, the glass-ceramics with special functions were obtained by selecting suitable composition of base glasses and controllable precipitation of special crystals. These glass-ceramics have special functions and may have wide variety of applications, such as wavelength convertor, solid state electrolyte, multi-windows imaging, and enhanced luminenscence of rare-earth ions. The main results are concluded as follows.1. According to the knowledge of Ge-S phase diagram and its thermal properties, the glass-ceramics only containingβ-GeS2 crystals are successfully prepared from GeS2 glass. It possesses permanent second order optical non-linearity, and the maximum of second-order optical nonlinearity was as high as 7.3 pm/V.2. Ga2S3 is added into GeS2 to modify the crystallization behavior, make the nucleation and crystallization process controllable based on the knowledge of nucleation-rate-like curve. IR-transparentβ-GeS2 nanocrystallized or only Ga2S3 precipitated glass ceramics were successfully fabricated from 90GeS2·10Ga2S3 or 80GeS2·20Ga2S3 glasses, respectively. The results indicated that, with the increasing Ga2S3 content, GeS2-Ga2S3 glasses displayed different behaviors of phase transformation. Based on thses results, a new structural model of GeS2-Ga2S3 glasses is established.3. The mechanism of crystallization was researched systematically on the quasi-ternary GeS2-Ga2S3-MX by adding Ag2S, Lil or CsCl into GeS2-Ga2S3 glasses. The IR-transmitting glass-ceramics with non-linear optical crystal AgGaGeS4 were prepared from the 70GeS2·15Ga2S3·15Ag2S glass and their largest second-order optical nonlinearity-5.79 pm/V can be comparable with those obtained by poling chalcogenide glasses. The nanocrystallized glass-ceramics with controllable properties were prepared from the 65GeS2·25Ga2S3·10LiI glass. The obtained IR-transparent glass-ceramics have enhanced thermo-mechanical and Li-ion-conducting properties, and also good second order optical non-linearity compared with that of base glass. To get a whole visible transparent chalcogenide glass, glasses is studied in detail. Nucleation-rate-like curves of the GeS2-Ga2S3-CsCl glasses were obtained to conduct a controllable crystallization of a series of glass-ceramics with excellent mid-IR transparency. In addition, the luminescence of Er-doped chalcogenide glass ceramics was enhanced more than one magnitude with the precipitation of crystals, suggesting a new way to infrared laser glasses.