| abstract |
This invention provides a reducing gas sensor which has a gas sensitive element of γ-ferric oxide (γ-Fe 2 O 3 ), a pair of electrodes and a heater element. The γ-ferric oxide is in the form of a thin film, a plate or a thin surface layer on a sintered plate of α-ferric oxide. This invention also provides a method of producing the reducing gas sensor, which includes the steps of firing γ-Fe 2 O 3 , γ-FeOOH or Fe 3 O 4 powder on a substrate and applying thereto a pair of electrodes and a heater element; or sintering alpha-ferric oxide (α-Fe 2 O 3 ) and reducing it to magnetite and oxidizing it at the surface thereof to γ-ferric oxide as a gas sensitive element. The sensitivity (R A /R G ) of the gas sensitive element of γ-ferric oxide is 10 to 130° at 270° C in an atmosphere containing 0.1 to 1 percent by volume propane gas, and the reducing gas sensor has high sensitivity and stability. |