| Summary: | 博士 === 國立成功大學 === 礦冶及材料科學研究所 === 75 === Single crystal and polyorystalline MgF2 optical ceramic materials have been inverstigated with relation-ship to their optical characteristies, hot-pressing me-chanism, kinetic equation for densification and mechanical strength. The findings of this study are given in the following:
(A) The color centers of MgF2 crystal can be enhanced by introducing the monovalent dopant of fluoride. It was due to the formation of fluoride vacancies. The efficiency of F-center production was proportional to the monovalent dopant concentration. The density of d F-center in doped crystals was proportional to the spuare root of irradiation time.
(B) AII models for the final stage densification may be expressed by the following formula, o=1=o'' exp ｛f(t)｝If they fit the equation o=1-o'' exp ｛-Mt｝ in the final stage densification, the model of densification may be determined by applying the grain growth law and the plot of equation o=1-o1'' exp ｛f(G)｝, This is supported by vertifications of the experimental results of hot-pressing fused sillica, magnesium fluoride and aluminum oxide.
(C) The densification of hot-pressing optical MgF2 ceramic was dominated by the plastic flow mechanicsm. The bending strength of the material was found to increase with grain growth in the initial stage. Therefore, it is inferred that the grains would respond with the following three stages, sequential-ly as: 1, the grains were deformed with simultaneous decrease of porosity. 2, the grains contact area of grains was increased, and 3, Via diffusion, the intergranular binding force was increased, and giving a higher bending strength. In addition, the optical transmittance was forund to be inversely proportional to the grain size.
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