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Proceedings Paper

Novel Zero-Expansion Materials For Precision Optical Substrates
Author(s): Yogesh Mehrotra; Dinesh K. Agrawal; V. S. Stubican
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Paper 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.

Paper Details

Date Published: 26 December 1984
PDF: 10 pages
Proc. SPIE 0505, Advances in Optical Materials, (26 December 1984); doi: 10.1117/12.964646
Show Author Affiliations
Yogesh Mehrotra, The Perkin-Elmer Corporation (United States)
Dinesh K. Agrawal, The Pennsylvania State University (United States)
V. S. Stubican, The Pennsylvania State University (United States)


Published in SPIE Proceedings Vol. 0505:
Advances in Optical Materials
Solomon Musikant, Editor(s)

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