Glass ceramic ZERODUR®: Even closer to zero thermal expansion: a review, part 1

Abstract

Observational astronomy has striven for better telescopes with higher resolutions from its start. This needs ever-larger mirrors with stable high precision surfaces. The extremely low expansion glass ceramic ZERODUR ® enables such mirrors with more than 50 years of significant improvements in size and quality since its development. We provide a survey of the progress achieved in the last 15 years. The narrowest coefficient of thermal expansion (CTE) tolerance is now AE7 ppb∕K. It is possible to adapt the material for lowest expansion to temperature-time courses given for special environments. At cryo temperatures, expansion is low and adaptable. Improved measurement capabilities allow for absolute CTE uncertainty of 3 ppb∕K and reproducibility of 1 ppb∕K (2σ). The influence of ionizing radiation on the surface figure integrity is subject to new investigations. Improved measurement capabilities increase the reliability of structure designs. Some outstanding examples are given for applications of ZERODUR in astronomy and in the very important high technology industry. The progress of thermal expansion homogeneity, the mechanical strength of ZERODUR, production capabilities in melting, precision machining, light-weighting, and dimensional metrology is presented in the second part of the paper. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Comprehensive review of the effects of ionizing radiations on the ZERODUR® glass ceramic

“…Macroscopically the interplay between these two coexisting phases results in material having a net macroscopic CTE close to 0 ppm.K−1 over temperature range that may be centered on T=20°C and spanning tens of degrees 1 . This supports form stability under thermal perturbations, but furthermore provides the critical features of high homogeneity, high isotropy and availability in large monolithic lightweigthed forms made of ZERODUR ® the material of choice for sensitive telescope mirrors, typically in orbiting missions 5 , 6 . For these reasons ZERODUR ® continues to be a widely employed material in space where high stability is needed.…”

“…1 This supports form stability under thermal perturbations, but furthermore provides the critical features of high homogeneity, high isotropy and availability in large monolithic lightweigthed forms made of ZERODUR ® the material of choice for sensitive telescope mirrors, typically in orbiting missions. 5,6 For these reasons ZERODUR ® continues to be a widely employed material in space where high stability is needed. It is a critical part of more than 40 orbiting missions 2,3 among these two NASA great observatories, Hubble-M2 and all Wolter mirrors on Chandra.…”

2023 Astrophotonics Roadmap: pathways to realizing multi-functional integrated astrophotonic instruments

“…This represents a technical challenge, especially for cavities designed around bulk materials such as SiO 2 (in the case of fiber-based etalons) or crystalline materials such as CaF 2 or MgF 2 (used in whispering-gallery-mode resonators) which have high coefficients of thermal expansion (CTE) and refractive index thermal coefficients (dn/dT). Even 'air-gap' etalon designs, which typically have spacers manufactured out of low-expansion materials such as Zerodur or ULE [460][461][462], still require thermal isolation and precise temperature control to maintain spectral stability (though not at the level of more standard glass materials). At the required level of control, even changes in the amount of injected light must be considered to avoid absorption-driven thermal variations.…”

Integration of negative, zero and positive linear thermal expansion makes borate optical crystals light transmission temperature-independent

“…, in metallic glass, 1 Invar alloy, 2 PbTiO 3 , 3 LaCu 3 Fe 4 O 12 , 4 cupric oxide 5 and BiNiO 3 , 6 but are also widely used to eliminate harmful thermal stress in devices and shield thermal noise in signal transmissions, such as those for fuel cells 7 and large telescopes. 8 To date, the manipulation and application of NTE or ZTE materials have mostly focused on chemical composition regulation, including multiphase composites, 9 chemical element doping, 10 guest molecule introduction 11,12 and defect introduction. 13 Here, we propose to modulate the anomalous thermal expansion in materials from another avenue, i.e.…”