Appeal No. 2006-1218
Application No. 10/601,884
preferably has a spinel crystal structure. Spinel is a metallic
oxide crystal form having the general formula of AB2O4 where A is
a 2+ cation occupying tetrahedral lattice sites in an oxygen
cubic close packed structure and B is a 3+ cation occupying
octahedral lattice sites. The preferred metals in the spinel
structure are magnesium and aluminum (page 1, line 19 – page 2,
line 4). Particularly, the claims are drawn to a spinel product
essentially free of sintering aids having a porosity of less
than 0.2% and a particular grain size.
Further details regarding this subject matter are set forth
in representative independent claims 1 and 19 which read as
follows:
1. A product that is essentially devoid of a sintering aid and
its components, said product comprising spinel that has porosity
of less than 0.2%, said spinel is transparent to light having
wavelengths in the range of 0.3-5.5 microns and said spinel
having transparency in excess of 50% for a thickness of 1 mm,
its spinel grains are within about 300% of the size of an
average grain and is devoid of grains larger than about 1 mm.
19. A magnesium aluminate spinel sintered product that is
essentially devoid of a sintering aid and its components, that
has porosity of less than 0.2%, has uniform grain size wherein
the grains are less than 300% of the average grain size and is
devoid of grains larger than about 1 mm.
The reference set forth below is relied upon by the
Examiner as evidence of anticipation or obviousness:
Sellers et al. (Sellers) 3,768,990 Oct. 30, 1973
2
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