Gas sensor

Automotive vehicles with an internal combustion engine have an exhaust system including a pathway for exhaust gas to move away from the engine. Depending on the desired operating state, internal combustion engines can be operated with fuel/air ratios in which (1) the fuel constituent is present in a stoichiometric surplus (rich range), (2) the oxygen of the air constituent is stoichiometrically predominant (lean range), and (3) the fuel and air constituents satisfy stoichiometric requirements. The composition of the fuel-air mixture determines the composition of the exhaust gas. In the rich range, considerable quantities of nonburned or partially burned fuel are found, while the oxygen has been substantially consumed and has nearly disappeared. In the lean range, the ratios are reversed, and in a stoichiometric composition of the fuel-air mixture, both fuel and oxygen are minimized. Disclosed herein is a gas sensor and a method of making a gas sensor comprising disposing a reference electrode on an inner surface of an electrolyte; sputtering a sensing electrode on an outer surface of the electrolyte; sputtering a zirconia layer on a side of the sensing electrode opposite the electrolyte, wherein the zirconia layer has a thickness of about 20 nanometers to about 1 micrometer, and disposing a protective layer on a side of the zirconia layer opposite the sensing electrode.