Pyrolytic boron nitride crucible and method

An article as defined in 4 wherein the dopant is selected from the group consisting of carbon and/or oxygen or mixtures thereof.

A method of forming a pyrolytic boron nitride article comprising the steps of introducing vapors of ammonia and a gaseous boron halide in a suitable ratio into a heated furnace reactor to cause boron nitride to be deposited in layers on a substrate, injecting at least one gaseous dopant into the furnace at controlled periodic interval(s) such that at least two selected layers of boron nitride are doped with said gaseous dopant(s) to at least a minimum concentration of 2 atomic wt % at a depth ranging from 1000 to 2000 angstroms in each selected layer, controlling the interval injection to space the selected layers from about 0.1 micron to 100 microns apart and separating the article from the substrate such that upon the application of stress in a direction substantially normal to the plane of deposition for the boron nitride layers peeling will be induced to occur in a doped layer along a fracture plane in which dopant is present on both sides of the fracture plane.

An article composed of layers of pyrolytic boron nitride (PBN) separated by layers of PBN doped with one or more elements selected from Group 1-6 of the periodic table, transition metals, rare earth metals, or combinations thereof such that the dopant is in a concentration in each of the doped layers above at least 2 atomic weight % at a depth ranging from about 1000-2000 angstroms measured from the surface of a peeled layer to induce peeling in each of the doped layers in a given sequence upon a build up of internal stress along a fracture plane in the peeled layer in which dopant is present on both sides of the fracture plane and with each of the doped layers being spaced at least one tenth of one micron apart.

An article as defined in 15 wherein the dopant is selected from the group consisting of carbon and/or oxygen or mixtures thereof.

An article composed of layers of pyrolytic boron nitride (PBN) separated by layers of PBN doped with one or more elements selected from Group 1-6 of the periodic table, transition metals, rare earth metals or combinations thereof such that the dopant is in a concentration above at least 2 atomic weight % at a depth ranging from about 1000-2000 angstroms measured from the peeled layer and with the thickness of the doped layers being varied relative to one another and being spaced at least one tenth of one micron apart to cause peeling of the doped layers to occur in a given sequence upon a build up of internal stress along a fracture plane in each peeled layer in which dopant is present on both sides of the fracture plane.

An article as defined in 22 wherein the dopant is selected from the group consisting of carbon and/or oxygen or mixtures thereof.