ZERODUR

ZERODUR

ZERODUR® is a glass ceramic characterized by a phase of evenly distributed nano-crystals within a residual glass phase. It contains around 75 weight percent crystalline phase with a high quartz structure. The crystal structure has a negative linear thermal expansion, while the other glass phase has a positive linear thermal expansion. The material is adjusted in a way that the positive thermal expansion of the glass phase and the negative thermal expansion of crystal structure effectively neutralize each other. The crystals are typically only 50 nm in diameter, and ZERODUR appears reasonably transparent because the refractive indices of the two phases are almost identical. The most important properties of zerodur are:  Nearly zero thermal expansion Excellent homogeneity High internal quality Outstanding chemical stability Polishable to a high accuracy Good processing behavior Low helium permeability Figure 1&2 and table 1 give an overview of ZERODUR’s properties.  Figure 1: External transmittance curve of ZERODUR at sample thickness of 5 mm and 25 mm. Figure 2: Thermal expansion coefficient curve of ZERODUR as a function of temperature. Optical Properties Wavelength(um) 656.27 643.85 587.56 546.07 486.13 479.99 435.83 Designated Letter C C' d e F F' g Refractive Index 1.5394 1.5399 1.5424 1.5447 1.5491 1.5497 1.5544 AbbeNumber 56.1 55.9 Mechanical Properties and Chemical Properties Density(g/cm3) Poisson's Ratio KnoopHardness Young's Moduluds (GPa) AcidResistance Class AlkaliResistance Class ClimaticResistance Class StainResistance Class 2.53 0.24 620 90.3 1 1 1 0 Table 1:ZERODUR Properties Low Expansion Materials :   Fused Silica ZERODUR® Corning Low Expansion Glass, Pyrex® ULE® titanium silica glass, VYCOR® brand glass and CLERACREAM®-Z ZERODUR® is a registered trademark of Schott Glass Technologies.