Appeal No. 2002-0258
Application No. 09/254,402
We find that Liu teaches a standard porous diffusion barrier
with a pinhole through which exhaust gases diffuse into a chamber
above the electrode (Column 7, lines 29-41). We find that Garzon
teaches the use of a diffusion of oxygen through a mixed
conducting layer which provides improved sensor performance vis-a-
vis aperture diffusion (column 2, lines 59-66). Accordingly, we
agree with the examiner that one of ordinary skill in the art at
the time the invention was made would have been motivated to
exchange pinholed porous layer 126 with a mixed conducting layer
as taught by Garzon.
We note that the examiner terms reference numeral 138 of Liu
as an insulating layer. We find that reference numeral 138 is a
ceramic spacer (column 7, lines 38-39) which defines a gas
compartment. While the spacer may be electrically insulating, the
defined compartment (and the electrode) is separated from the
exhaust gas only by a diffusion barrier 126 with a diffusion
aperture 128 (or, if substituted by Garzon, only by the mixed
conducting layer) allowing direct passage of exhaust gas by
diffusion through the aperture, or oxygen by transport through the
layer.
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