Light-transmitting silicon nitride
 A polycrystalline silicon nitride body having a density of at least 99.5% of the theoretical density of silicon nitride, a thickness ranging from about 0.15 mm up to but less than 0.4 mm, a minimum in-line transmission of about 5% of radiant energy at wavelengths ranging from about 0.9 micron to about 2.5 microns, and a minimum in-line transmission of about 10% at wavelengths ranging from about 2.5 microns to about 4.5 microns. 
General Electric Company
C
C04B
inventional
Svante John A. Charles D.
Prochazka Palm Greskovich