Auer Lighting borosilicate glass SUPRAX® 8488 is a suitable material for microwave applications, e.g. as a lamp cover glass.
The measurement below shows the half-value layer for SUPRAX® 8488, a special borosilicate glass from Auer Lighting. The half-value layer is a widely used indicated value for microwave properties. It describes the depth in an absorbing material at which the power of a propagating TEM (Transversal Electro Magnetic) wave is reduced to 50% of its initial value by deposition as heat. The measurement covers the temperature range from 25 °C to 400 °C and has been taken at 2.466 GHz.
Microwave properties of SUPRAX® 8488
Dielectric constant ε’
5.1 ± 0.1
5.7 ± 0.1
Dissipation factor ε’’
0.050 ± 0.005
0.26 ± 0.03
0.010 ± 0.001
0.045 ± 0.004
TEM half-value layer (mm)
610 ± 50
125 ± 10
For a thin window, the fraction of the travelling wave power deposited in the window can be simply estimated by:
0.693 · window thickness
PowerFraction ≈ ____________________________
For a 3 mm thick SUPRAX® 8488 window at 20°C this gives a power deposition of ~0.3% of the magnetron output power.
In every case it is still in responsibility of the manufacturer of the microwave oven to design the product in a safe way. He has to take care for avoiding hot spots in the complete system, which will damage every glass material.