HOQ® 310

Heraeus HOQ® 310 is manufactured by fusion of natural quartz crystals in an electrically heated furnace. HOQ® 310 is economically priced and has been developed especially for applications in the technical optics field. Compared with „typical“ optical glasses it provides a unique combination of attractive properties:

Combined with a low bubble content and an attractive price HOQ® 310 is the preferred material for lower precision optical applications in a hostile environment, e.g. high temperature and/or thermal shock loads, pressure loads, chemically aggressive atmosphere, etc., such as inspection and/or illumination windows, cover plates, windows for pressurized cabins, etc.

For general technical data please refer to our data sheet POL-O/107E "Quartz Glass for Optics - Data and Properties".

(Bubbles and Inclusions ≤ 0.08 mm diameter are disregarded)

Bubble class : 2...3 (as per DIN 58927 2/70)
i.e. total bubble cross section within the volume is ≤ 0.5 mm

Bubbles according to DIN ISO 10100
HOQ® 310 :

• 1 / 2*0,63 for pieces < 6
• 1 / 2*1,0 for pieces 6 - 30

Inclusions :
None

Spectral Transmission
The transmission (including Fresnel reflection losses at two uncoated surfaces) for a 10 mm path length is shown in the figure.

Refractive Index
n_C ( λ = 656.3 nm ) 1.45646
n_d ( λ = 587.6 nm ) 1.45856
n_F ( λ = 486.1 nm ) 1.46324
n_g ( λ = 435.8 nm ) 1.46681

Dispersion
Abbe-Constant ^V_d= 67.6 ± 0.5
Principal Dispersion n_F - n_C = 0.00678

OH-Content
OH-Content ≤ 30 ppm

Accordingly, there are weak infra-red absorption bands around 1.39 µm, 2.2 µm, and 2.72 µm.

Birefringence
The birefringence remaining in an optical element is caused by mechanical internal stresses. It depends up to a great extent on the shape and size of the element.

Residual strain
HOQ® 310 ≤ 10 nm/cm - across 80% of dia.
10-20 nm/cm - at the rim area
Birefringence constant 3.61 ∙ 0.05 nm / (cm ∙ bar)
HOQ® 310 is delivered annealed. When pieces of fused quartz are being worked in the raw state, "cutting stresses" often occur along edges and at corners; these disappear again during subsequent fine working or by light etching with hydrofluoric acid.

Viscosity
The viscosity of fused quartz decreases very steadily with increasing temperature. The characteristic temperatures are solely defined by viscosity η

Annealing point(lg η = 13.0) *) ca. 1220°C

Strain point (lg η = 14.5) *) ca. 1125°C

Maximum temperature (continuous) ca. 1150°C

Maximum temperature (limited life) ca. 1300°C

*) Viscosity in dPa • s

Coefficient of Thermal Expansion
Mean linear CTE α in various intervals

∆T (°C) α (K-1)

0...100 0.51 • 10^-6

0...200 0.58 • 10^-6

0...300 0.59 • 10^-6

0...600 0.54 • 10^-6

0...900 0.48 • 10^-6

-50. ..0 0.27 • 10^-6

The extremely low coefficient of thermal expansion (CTE) results in an excellent thermal shock resistance, much superior to that of ordinary glasses or ceramics.

Heat conductivity λ

T (°C) λ (W / (K • m) )

20 - 1.38

100 - 1.46

200 - 1.55

300 - 1.67

400 - 1.84

950 - 2.68

Mean specific heat Cp
T (°C) - Cp (J / (kg • K))

0...100 - 772

0...500 - 964

0...900 - 1052

The following data are valid for room temperature

Density - - - g/cm³ - - - 2.20

Young's modulus (at 20°C) - - - N/mm² - - - 7.25 •10⁴

Poisson's ratio - - - -- - - - 0.17

Compressive strength - - - N/mm² - - - 1150

Tensile strength - - - N/mm² - - - approx. 50

Knoop hardness (1 N load) - - - N/mm² - - - 5800...6200

The "real world" tensile strength is almost entirely determined by the surface quality of a piece. The tensile strength value listed above is a typical average value for a round disk with mechanically polished main faces and fine ground circumference. For strength calculations a sufficiently high safety factor must

be included.

Chemical Resistance
Fused quartz is outstandingly resistant to water, salt solutions, acids, and alkaline solutions.

Hydrolytic resistance as

per DIN 12 111

1. Hydrolysis class:

Base discharge

Resistance to acids as

per DIN 12 116

1. Acid class:

Weight loss <0.1 mg/dm²

surface area

Resistance to alkaline solutions

as per DIN 52 322

1. Alkaline solution class:

Weight loss approx. 50 mg/dm²

surface area

Impurities
Typical trace impurities in fused quartz HOQ® 310 (in weight ppm)

Al - - - 20 - - - Li - - - 1

Ca - - - 1 - - - Mg - - - 0.1

Cr - - - 0.1 - - - Na - - - 1

Cu - - - 0.1 - - - Ti - - - 1

Fe - - - 0.8 - - - OH - - - 30

K - - - 0.8