1 April 1986 New Materials For Precision Optics
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A novel family of germania-modified cordierite ceramics has been developed for the fabrication of precision optical components. Compositions in this family possess zero average coefficient of thermal expansion (CTE) over selected temperature regions. Moreover, the zero CTE can be tailored to a desired temperature range of operation by varying the relative proportions of Ge02 and Si02 in the modified cordierite structure. Thermal diffusivity of these ceramics is more than twice that of the ULE glass, a current state-of-the-art material for precision mirror substrates. In addition, germanium-cordierites possess high specific stiffness and low thermal-moment/rigidity ratio. Control-lable fine-grained structure enables good polishability and offers the potential for an optical quality surface. These thermal and mechanical properties make Ge-cordierites an excellent family of materials for optical and structural applications. The theoretical basis for germania substitution for silica in the pure cordierite structure has been examined. Material characteristics including solid solubility and sinterability have been considered. All the germanium-cordierite compositions presented in this study are morphologically single-phase and microstructurally homogeneous materials. These properties along with tailorable zero CTE characteristics offer the potential of employing cordierites for high precision optics.
Yogesh Mehrotra, Yogesh Mehrotra, Dinesh K. Agrawal, Dinesh K. Agrawal, Vladimir S. Stubican, Vladimir S. Stubican, } "New Materials For Precision Optics," Optical Engineering 25(4), 254513 (1 April 1986). https://doi.org/10.1117/12.7973853 . Submission:

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