CORNING® 8250 KOVAR SEALING

Schott® borosilicate glass 8250 is widely used as a Kovar Sealing glass. In addition to machine drawn sizes available from Schott®, Glass Dynamics LLC has the ability to produce "redrawn" sizes from .010 to .50" diameters in small lots of 10 to 15 pounds. Our current OVER STOCK BARGIN sizes can be viewed below. You can also view Corning® 7052 Kovar Sealing glass, Corning® 7056 Kovar Sealing glass and Corning® 7720 Nonex Tungsten Sealing glass.

Kovar Sealing Glass: Schott® 8250
Glass Code: Schott® 8250
Glass Type/Application

Borosilicate glass for sealing KOVAR metal and molybdenum, electrically highly insulating
X-ray tubes, transmitting tubes, image amplifier tubes, HE-NE-laser, clad tube for optical fibres, ozone generators

Physical Data
Coefficient of mean linear thermal expansion
α (20 °C; 300 °C) acc. to ISO 7991
5,0
10-6K-1
Transformation Temperature Tg
490
°C
Glass Temperature at Viscosity η in dPa · s 1013 (Annealing Point)
500
°C
107.6 (Softening Point)
720
°C
104 (Working Point)
1055
°C
Stress-Optical Coefficient K
3,6
10-6mm2· N-1
Density ρ at 25°C
2,28
g · cm-3
Modulus of Elasticity E (Young's Modulus)
64
103N · mm-2
Poisson's Ratio µ
0,21
Thermal Conductivity λw at 90 °C
1,2
W · m-1 · K-1
Log of the electric volume resistivity (Ω · cm) @ 250 °C
10
350 °C
8,3
tk100
375
°C
Dielectric Constant ε for 1 MHz at 25 °C
4,9
Dielectric Loss Factor tan δ for 1 MHz at 25 °C
22
10-4
Refractive index nd (λ =587.6nm)
1,487
Chemical Resistance
Hydrolytic Resistance (ISO 719)
Class
HGB 3
Acid Resistance (DIN 12116)
Class
S 4
Alkali Resistance (ISO 695)
Class
A 3
Chemical Compostion: Components in Approx. Weight %
SiO2
B2O3
AI2O3
Na2O
K2O
Li2O
ZnO
69
18,5
3
1
7,5
0,5
0,5
The heavy metal content for the elements lead, cadmium, mercury and hexavalent chromium is below 100 ppm.

 

Redrawn: Over Stock Bargin Sizes
Corning® 9741
GE 010 Lead
Schott® 8337B
OD 1.145" x ID 1.075"
OD 5.75mm x ID 4.5mm
OD 12.30mm x Wall .50mm
OD 2.55mm x ID 1.22mm
OD 2.80mm x ID 2.25mm
2015 © Glass Dynamics, LLC.
Designed by Kim Kelly