Silicon-nitride-containing separating layer having high hardness
The invention relates to a shaped body comprising a substrate with a firmly adhering separating layer, wherein the separating layer comprises 92-98 wt. % silicon nitride (Si 3 N 4 ) and 2-8 wt. % silicon dioxide (SiO 2 ) and wherein the separating layer has a total oxygen content of ≦8 wt. % and a hardness of at least 10 HB 2.5/3 according to DIN EN ISO 6506-1.
1. Shaped body comprising a substrate with a firmly adhering separating layer, wherein the separating layer comprises 92-98 wt. % silicon nitride (Si 3 N 4 ) and 2-8 wt. % silicon dioxide (SiO 2 ) and wherein the separating layer has a total oxygen content of ≦8 wt. % and a hardness of at least 10 HB 2.5/3 according to DIN EN ISO 6506-1.
2. The shaped body according to claim 1 , wherein the separating layer furthermore contains a residual content of a dopant in the form of a flux.
3. The shaped body according to claim 2 , wherein the dopant comprises an alkali metal compound.
4. The shaped body according to claim 3 , wherein the fraction of the dopant expressed as the alkali metal content of the separating layer is up to 150 ppm.
5. The shaped body according to claim 1 , wherein the total oxygen content of the separating layer is <5 wt. %.
6. The shaped body according to claim 1 , wherein the separating layer contains 94-98 wt. % Si 3 N 4 and 2-6 wt. % SiO 2 .
7. The shaped body according to claim 1 , wherein the hardness of the separating layer is at least 15 HBW 2.5/3 according to DIN EN ISO 6506-1.
8. The shaped body according to claim 1 , wherein the substrate consists of fused silica.