Abstract Quartz glass element, such as a diffusion tube useful in the production of semiconductor elements, capable of forming an outer layer of uniformly fine crystalline silica such as cristobalite or tridymite when heated to a temperature at which such crystalline silica forms containing crystallization promoting nuclei having a rate of diffusion in quartz glass less than that of sodium at elevated temperatures. Such nuclei are present in the outer half of the element wall and the maximum concentration of such nuclei is at the surface of the element and then diminishes inwardly. When the quartz glass element is exposed to elevated temperatures, the nuclei promotes the formation of the outer layer of uniformly fine crystalline silica which imparts thermal dimensional stability for extended periods of use at elevated temperatures.
Element of claim 1 wherein said nuclei are selected from the group of a Group IV element, boron, aluminum, phosphorus, antimony, zinc, magnesium, calcium, gallium, and mixtures of the foregoing.
Claim 2
Dependent Claim
15 words
Element of claim 1 wherein said element is a diffusion tube for producing semiconductor elements.
Claim 3
Dependent Claim
22 words
Element of claim 1 wherein the surface concentration of said nuclei is from about 1.1014 to about 5.1017 nuclei per sq. cm.
Claim 4
Dependent Claim
18 words
Element of claim 1 wherein the depth of said nuclei is from about 5 to about 200 millimicrons.
Claim 5
Dependent Claim
18 words
Element of claim 1 wherein the depth of said nuclei is from about 5 to about 100 millimicrons.
Claim 6
Dependent Claim
18 words
Element of claim 1 wherein the depth of said nuclei is from about 10 to about 80 millimicrons.
Claim 7
Dependent Claim
21 words
Element of claim 1 having said tensilely stressed outer layer formed by heating to a temperature at which crystalline silica forms.
Claim 8
Dependent Claim
17 words
Element of claim 1 wherein said crystalline silica is selected from the group of cristobalite and tridymite.
Claim 9
Dependent Claim
22 words
Diffusion tube of claim 3 having said tensilely stressed outer layer formed by heating to a temperature at which crystalline silica forms.
Claim 10
Dependent Claim
19 words
Diffusion tube of claim 3 wherein only the central outer portion thereof is provided with said crystallization promoting nuclei.