An additive manufacturing process includes forming an object material stack using sheet materials without use of binder material between the sheet materials and forming features of the cross-sectional layers of a 3D object in the corresponding sheet materials. Another process involves forming features of the cross-sectional layers of a 3D object in soot layers of a laminated soot sheet. A manufactured article includes three or more glass layers laminated together without any binder material between the glass layers. At least one of the glass layers is composed of silica or doped silica, and at least one feature is formed in at least one of the glass layers.

A doped silica-titania glass article is provided that includes a glass article having a glass composition comprising (i) a silica-titania base glass, (ii) a fluorine dopant, and (iii) a second dopant. The fluorine dopant has a concentration of fluorine of up to 5 wt. % and the second dopant comprises one or more oxides selected from the group consisting of Al, Nb, Ta, B, Na, K, Mg, Ca and Li oxides at a total oxide concentration from 50 ppm to 6 wt. %. Further, the glass article has an expansivity slope of less than 0.5 ppb/K.sup.2 at 20 C. The second dopant can be optional. The composition of the glass article may also contain an OH concentration of less than 100 ppm.

The Ti.sup.3+ ions present in Ti-doped silica glass cause a brown staining of the glass, causing inspection of the lens to become more difficult. Known methods for reducing Ti.sup.3+ ions in favor of Ti.sup.4+ ions in Ti-doped silica glass include a sufficiently high proportion of OH-groups and carrying out an oxygen treatment prior to vitrification, which both have disadvantages. In order to provide a cost-efficient production method for Ti-doped silica glass, which at a hydroxyl group content of less than 120 ppm shows an internal transmittance (sample thickness 10 mm) of at least 70% in the wavelength range of 400 nm to 1000 nm, the TiO.sub.2SiO.sub.2 soot body is subjected to a conditioning treatment with a nitrogen oxide prior to vitrification. The blank produced in this way from Ti-doped silica glass has the ratio Ti.sup.3+/Ti.sup.4+510.sup.4.

A method for homogenizing glass includes the method: providing a cylindrical blank composed of the glass having a cylindrical outer surface that extends along a longitudinal axis of the blank between a first end face and a second end face, forming a shear zone in the blank by softening a longitudinal section of the blank and subjecting it to a thermal-mechanical intermixing treatment, and displacing the shear zone along the longitudinal axis of the blank. The displacement of the shear zone along the longitudinal axis of the blank is superimposed by a simultaneous oscillating motion of the shear zone along the longitudinal axis of the blank. The first end of the blank is rotated at a first rotational speed and the second end of the blank is rotated at a second rotational speed. An oscillating motion of the shear zone is generated by periodically varying the first and/or second rotational speed.

Ultralow expansion titania-silica glass. The glass has high hydroxyl content and optionally include one or more dopants. Representative optional dopants include boron, alkali elements, alkaline earth elements or metals such as Nb, Ta, Al, Mn, Sn Cu and Sn. The glass is prepared by a process that includes steam consolidation to increase the hydroxyl content. The high hydroxyl content or combination of dopant(s) and high hydroxyl content lowers the fictive temperature of the glass to provide a glass having a very low coefficient of thermal expansion (CTE), low fictive temperature (T.sub.f), and low expansivity slope.

A method for producing a silica glass blank co-doped with titanium and fluorine for use in EUV lithography includes (a) producing a TiO.sub.2SiO.sub.2 soot body by flame hydrolysis of silicon- and titanium-containing precursor substances, (b) fluorinating the TiO.sub.2SiO.sub.2 soot body to form a fluorine-doped TiO.sub.2SiO.sub.2 soot body, (c) treating the fluorine-doped TiO.sub.2SiO.sub.2 soot body in a water vapor-containing atmosphere to form a conditioned soot body, and (d) vitrifying the conditioned soot body to form the blank. The blank has an internal transmission of at least 60% in the wavelength range of 400 to 700 nm at a sample thickness of 10 mm, a mean OH content in the range of 10 to 100 wt. ppm and a mean fluorine content in the range of 2,500 to 10,000 wt. ppm. Titanium is present in the blank in the oxidation forms Ti3.sup.+ and Ti.sup.4+.

A blank made of titanium-doped silica glass for a mirror substrate for use in EUV lithography is provided. The blank includes a surface portion to be provided with a reflective film and having an optically used area (CA) over which a coefficient of thermal expansion (CTE) has a two-dimensional inhomogeneity (dCTE) distribution profile averaged over a thickness of the blank. A maximum inhomogeneity (dCTE.sub.max) of less than 5 ppb/K is defined as a difference between a CTE maximum value and a CTE minimum value. The dCTE.sub.max is at least 0.5 ppb/K. The CA forms a non-circular area having a centroid. The dCTE distribution profile is not rotation-symmetrical and is defined over the CA, such that straight profile sections normalized to a unit length and extending through the centroid of the area yield a dCTE family of curves forming a curve band with a bandwidth of less than 0.5dCTE.sub.max.

A process of forming a titania-silica glass body, the process including exposing a titania-doped silica soot body to a constant steam pressure step during which the partial steam pressure is at a first partial pressure of steam P1 that is from about 0 Torr to about 760 Torr and exposing the soot body to a ramp-up steam pressure step during which the partial steam pressure increases from the first partial pressure of steam P1 to a second partial pressure of steam P2, the second partial pressure of steam P2 being from about 50 Torr to about 760 Torr. The second partial pressure of steam P2 being greater than the first partial pressure of steam P1. The process further including heating the soot body during the constant steam pressure step and during the ramp-up steam pressure step and increasing the temperature during at least one of the constant steam pressure step and the ramp-up steam pressure step.