Patent ID: 7048844

Claim:
A sensor comprising: a pump cell comprising: an inner pump electrode; an outer pump electrode; a pump cell electrolyte layer interposed between the inner pump electrode and the outer pump electrode; and a cell isolation layer disposed on the inner pump electrode on a side opposite the pump cell electrolyte, a reference cell in operable communication with the pump cell, the reference cell comprising an outer reference electrode and an inner reference electrode, and a reference cell electrolyte interposed between the outer reference electrode and the inner reference electrode; and a diffusion limiting material flanking both sides of a chamber formed between the cell isolation layer and a cell separation layer, wherein the cell separation layer comprises a via coaxial and in fluid communication with the inner pump electrode, the diffusing limiting material, and the outer reference electrode, and wherein the diffusion limiting material has a gas permeability such that the limiting current of oxygen in air is about 0.05 mA to about 5 mA per cm 2 of pump electrode area said diffusion limiting material comprising aluminum oxide wherein 45 wt % to about 55 wt % of said aluminum oxide has a first particle size distribution of about 4.5 micrometers to about 5.5 micrometers and the balance has a second particle size distribution of about 0.3 micrometers to about 0.7 micrometers.