Microwave characteristics of SUPRAX® 8488
Auer Lighting borosilicate glass SUPRAX® 8488 is a suitable material for microwave applications, e.g. as a lamp cover glass.
Half-Power Depth
The measurement below shows the half-power depth for SUPRAX® 8488, a special borosilicate glass from Auer Lighting. The half-power depth 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
| Temperature | 20 °C | 400 °C |
| Dielectric constant ε’ | 5.1 ± 0.1 | 5.7 ± 0.1 |
| Dissipation factor ε’’ | 0.050 ± 0.005 | 0.26 ± 0.03 |
| Loss tangent | 0.010 ± 0.001 | 0.045 ± 0.004 |
| TEM half-power depth (mm) | 610 ± 50 | 125 ± 10 |
Example
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 ≈ ____________________________
Half Power Depth
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.