Novel Zero-Expansion Materials For Precision Optical Substrates

Yogesh Mehrotra; Dinesh K. Agrawal; V. S. Stubican

doi:10.1117/12.964646

26 December 1984 Novel Zero-Expansion Materials For Precision Optical Substrates

Yogesh Mehrotra, Dinesh K. Agrawal, V. S. Stubican

Proceedings Volume 0505, Advances in Optical Materials; (1984) https://doi.org/10.1117/12.964646
Event: 28th Annual Technical Symposium, 1984, San Diego, United States

Abstract

A novel family of "germania-modified cordierite" ceramics has been developed for 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 ULETM 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. Controllable fine-grained structure enables good polishability and offers the potential for an optical quality surface. These thermal and mechanical properties make Ge-cordierite an excellent material for optical and structural applications. The theoretical basis for germania substitution for silica in the pure cordierite struc-ture 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.

Citation Download Citation

Yogesh Mehrotra, Dinesh K. Agrawal, and V. S. Stubican "Novel Zero-Expansion Materials For Precision Optical Substrates", Proc. SPIE 0505, Advances in Optical Materials, (26 December 1984); https://doi.org/10.1117/12.964646

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