Fused Silica Products for Technical Lamps

Quartz glass or fused silica is an irreplaceable material for many technical lamps. Learn more about how to find the best quartz glass or fused silica for your technical lamp application.

Quartz glass is the purest form of glass. It consists only of Silicon and Oxygen. Due to this unique chemical composition (single component glass) and the high purity – at Heraeus Conamic min. 99,999% SiO2 purity – quartz glass has excellent technical properties. In particular, the wide transmission spectrum from the ultraviolet, visible to infrared range (depending on grade between 160nm up to 4500nm) makes quartz glass an irreplaceable material for many technical lamps.

Fusion Processes for Technical Lamp Tubes

Heraeus is using different fusion methods for the manufacture of technical lamp tubes. In the following you find a short introduction to the methods:

Electric Fusion Process

Electric fusion is the most commonly used melting process for manufacturing quartz glass. Electric fusion is accomplished either by an electric gas discharge (arc melting) or by applying heat generated by electric resistance.

A further differentiation is made by selecting a continues or batch process. Single step electrically fused tubing is fabricated by pouring sand into the top of a vertical smelter that consists of a refractory metal crucible. At temperatures exceeding 1800°C the ordered micro- structure of the raw material changes into the irregular glass network, glass is formed. Through an outlet in the bottom of the crucible the glass is pulled directly in the shape of tubes or as a solid, a so-called ingot.

Electric fused quartz has the highest temperature resistance and highest viscosity of the vitreous silica types.

Flame Fusion Process

Flame fusion is the most traditional form to fuse quartz. A H2/O2-flame is used to fuse crystalline particles to fused quartz. Heraeus chemist Dr. Richard Küch was the first to use this method on an industrial scale over 100 years ago. For a continues process small grains of the raw material are constantly trickled into a flame and fused onto a glass rod, that is slowly removed as it grows. Flame fused quartz has better homogeneity and solarization resistance compared to electric fused quartz. 

Synthetic Fusion Process

Heraeus is using two different Synthetic Fusion Processes. More common (trough use for manufacturing pre-forms for Telecommunication Fiber) is the CVD-process or Soot process. In this process chemical precursors (e.g. OMCTS or SiCl4) are oxidized (burned) in a H2/O2 flame. The forming SiO2 is deposited on a rotating bait tube like smoke off a candle deposits on a stick above the flame. The soot body is then vitrified into a transparent glass body in a second process step. 

Second Fusion process is to manufacture solids in an OVD or DQ-process (direct quartz process). The process is comparable to the Flame Fusion process and differs in that a liquid chemical precursor (e.g. OMCTS) to be fused in the gas flame. 

Because the precursors are made in an industrial chemical process, the raw materials have exceptionally high purity. Glass made of these precursors has an alkali- and metal ion content in the parts per billion (ppb) range. Synthetic fused silica has the best transmission, the highest purity and the best solarization resistance of all vitreous silica types. 

Production Methods for Lamp Tubes

Heraeus is using different production methods for tubes manufacturing. In the following you find the differences methods:

  • Single Step Tubing
    The pulling of tubing directly from the melt is the most cost efficient production process. It is available only for electric fused quartz. The outlet of the crucible is ring shaped and the size of the forming tool determines the available dimensions of tubing (outer diameter, wall thickness). Because a change of the forming tool is not possible once the process started, the range of tube sizes per run is limited. A large amount of tubes must be drawn in order to justify using this process. Tubes produced in the single step process have tight tolerances and are most economic.
  • Multi Step Tubing:
    In this process a pre-form (usually a cylinder) is locally heated and redrawn into tubing. The cylinder is either formed directly or an ingot is reshaped into a cylinder. Because the reforming of glass is independent on the actual production route of the quartz glass, multistep tubing is available in electric and flame fused quartz as well as synthetic fused silica. Furthermore, the additional process-steps homogenize the material usually resulting in a lower bubble content. The available finished sizes depend solely on the size of the starting cylinder. The advantage of the multistep process is the high flexibility regarding starting material and finished sizes, as well as a relatively small batch size.

Material Selection Guide for Technical Lamp Applications

Heraeus offers many different quartz grades under various trademarks. The following table details these material grades and can offer guidance on which grades are suitable for specific applications.

Material Grades for Technical Lamps

Material Grade

Production Type

Application

Feature

Lamp Type

HLQ® 200

Electric

Infra red processing, UV curing, UV disinfection, projection lamps for SC and LCD stepper

Clear fused, low OH < 1 ppm available

Infra red lamps, low and medium pressure UV lamps, sleeves, metal halide lamps

HLQ® 210

Electric

Laser excitation, beauty and medical
high quality lamps

Clear fused, low OH < 1 ppm available, low bubble content, high homogeneity

Long arc cw and pulsed lamps, demanding short arc lamps

HLQ® 270

Electric

Lamps for digital projection, stage and studio, cinema

Clear fused, low OH < 1 ppm available, high homogeneity, low alkaline content, high recrystallisation resistance

High and ultra-high pressure short arc lamps, demanding metal halide lamps, demanding cw and pulsed long arc lamps

HLQ® 235

Electric

UV disinfection, projection lamps for SC and LCD stepper

Doped, ozone-free*, low OH < 1 ppm available

Ozone-free low and medium pressure UV lamps, short arc lamps

HLQ® 250

Electric

UV tanning

Doped, ozone-free*, low OH < 1 ppm available

FDA conform ozone-free lamps

HLQ® 382

Electric

Excitation lamps e.g. for laser fusion

doped, uv-free**

Long arc lamps

Heralux® plus / vuv

Flame

UV curing, UV applications, laser excitation

Clear fused, almost free of bubbles, good UV transmission, high resitance to UV radiation

Medium pressure UV lamps, long arc lamps

M215 / M235

Flame

Projection lamps for SC and LCD stepper

Doped, ozone-free*, free of striae

Ozone-free short arc lamps

M 235 plus

Flame

Projection lamps for SC and LCD stepper, laser exication, medical

Doped, ozone-free*, high homogeneity, free of striae

High intense ozone-free short arc lamps, ozone-free long arc lamps

M 382 plus

Flame

Laser excitation, beauty and medical

Doped, uv-free**, high homogeneity, free of striae

Long arc cw and pulsed lamps, intense pulsed lamps

Suprasil® 030

Synthetic

Disinfection and purification

High purity, high UV transmission

Medium pressure lamps for deep UV, long life-sleeves for deep UV

Suprasil® 130

Synthetic

Ozone generation, grease destruction, disinfection and purification, production of ultra pure water

High purity, high UV transmission, high resistance to short-wave UV radiation

185 nm low pressure lamps, medium pressure lamps for deep UV

Suprasil® 300

Synthetic

Spectroscopy, broad band optical applications

Highest purity, OH < 1 ppm, free of bubbles, highest transmission from UV to IR spectral range

Deuterium lamps, high intense mircro-wave lamps

Suprasil® 310

Synthetic

Surface cleaning in SC and LCD processing, photochemical vapour deposition, surface activation, photochemistry

Highest purity, free of bubbles, highest UV transmission, resistant to short- wave UV radiation

172 nm Xe-excimer lamps, very demanding long arc lamps

Spectrosil® 2000

Synthetic

Highest intense VUV lamps

Highest purity, free of bubbles, highest UV transmission, resistant to short- wave UV radiation

Highest intense UV-C short arc lamps

Purasil®

Synthetic

Disinfection and purification

High purity, high UV transmission

Long life-sleeves for deep UV

Purasil® XP

Synthetic

Disinfection and purification

High purity, high UV transmission, high resistance to short-wave UV radiation

Longest life-sleeves for deep UV

* (Wavelengths, where ozone forms are absorbed)

** (UV wavelengths are absorbed)

Tools and Services

In the selection process for the most suitable fused silica grade the transmission performance is among the first criteria. Please check our transmission calculator. As an additional service, we offer the possibility to search our portfolio for existing part numbers.

Downloads

  • Brochure: Quartz Glass for Lamp Manufacturing

    Download
  • Data Sheet: Behavior of various elements and compounds towards fused silica

    Download