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A thick film type oxygen sensor has been developed. It has the unique structure and principle to achieve the fast light off and a compact configuration. The main part of the uniqueness is the self generation of oxygen from exhaust gas, as the reference. In another words, this does not require fresh air from atmosphere as the conventional thimble type oxygen sensor and no output is shifted down by the change of the reference oxygen partial pressure. The other advantage is monolithic nature of the sensing element and the heater, which makes the sensor start working about in 10 seconds with small wattage. The combination of these two key technologies enables the oxygen sensor to be small and free from location issue.

The gas pressure sintering (GPS) process of silicon nitride is capable of producing sintered material of better quality than that obtained with the conventional normal sintering methods, and can be performed in a procedure simpler than the HIP method. These features of the GPS process have made it a promising manufacturing process for high quality silicon nitride ceramics. However, because sintering is performed in a high pressure atmosphere in this process, a 2-step sintering method had to be developed before applying it to practical industrial manufacture. The gas pressure sintered silicon nitride (GPSSN) ceramics densified to high density have already been used in turbocharger rotors for automotive applications, cutting tools, and bearing balls for industrial applications, etc., and have been highly evaluated for high strength and reliability.