Feature Article 2
Kyocera’s Fine Ceramic Technology Contributes to Global Environmental Preservation
Contribution to Cleaning of Diesel Car Emissions


Diesel vehicles make up approximately 30% of all cars produced in the world. They emit less CO2 one of the causes of climate change than gasoline cars and have high power and excellent durability. Because of those advantages, there is growing demand for diesel cars in the world, particularly in Europe.

In Europe, there are many environmentally advanced countries engaged in active reduction of air pollutants which apply strict regulations to soot emission of diesel cars. Diesel cars in Europe are obligated to have pollution control equipment such as diesel particulate filters (DPFs) that capture soot in the exhaust gas. In order to check if the DPF is properly working, sensors to detect soot contained in the exhaust gas are essential. However, presently there are no sensor elements that can precisely detect soot. Therefore, development of such high-performance sensors is urgent.

Kyocera developed a soot detection sensor element that has high reliability in high temperatures greater than 500C for the first time in the world* by using its own metal material technology accumulated over many years.

*Based on research by Kyocera (as of October 1, 2015)

Development of a Soot Sensor Element Capable of Detecting Soot in Temperatures Greater than 500C without the use of Platinum

Since a soot sensor element needs to be installed near the engine, it needs to be made of a material with excellent heat and acid resistance. In general, platinum is used for such sensor elements. However, when the temperature of the exhaust gas exceeds 500C, platinum and soot cause a catalytic reaction resulting in the failure to detect soot accurately.

Facing this problem, Kyocera developed a new alloy conductor featuring performance equivalent to that of platinum without using this metal for the first time in the world by utilizing material and production process technologies cultivated in our development of ceramic packages which boast the world’s top share (approx. 70%). Furthermore, we realized downsizing and durability enhancement of the soot sensor element by sintering ceramics and the alloy conductor in multiple layers.

Photo: Sensor part of the soot sensor element Photo: Soot-sensing element

Sensor part of the soot sensor element

Soot-sensing element

Image:  Structure of the soot sensor element

Structure of the soot sensor element

Mechanism of soot detection

Soot conducts electricity, and by using this characteristic, the sensor detects soot with electrodes that are arranged in a comb-like pattern and insulated so that no electricity flows in the electrodes unless soot is attached. When soot is attached among the electrodes, electricity flows, and the amount of soot contained in the exhaust gas is detected. A heater is installed inside the element so it periodically burns the soot attached to the electrodes and thus allows repeated and accurate measurement.

Mechanism of soot detection

Mechanism of soot detection

Awarded the Semi Grand Prix of the CEATEC AWARD 2015 in the Green Innovation Category

Photo: CEATEC AWARD 2015
Semi Grand Prix

Semi Grand Prix

The soot sensor element developed by Kyocera won the Semi Grand Prix of the CEATEC AWARD 2015 in the Green Innovation Category at CEATEC JAPAN, one of Asia’s largest comprehensive exhibitions of advanced IT and electronics held in Japan every October. Products and technologies on exhibit at CEATEC JAPAN that show particularly excellent innovation are given CEATEC AWARDS. The alloy conductor, a new material developed by Kyocera to replace platinum, was used to make the element capable of detecting soot under high temperatures greater than 500C. This innovation was highly evaluated and led to the awarding of the Semi Grand Prix Award.

Comments of the staff in charge of the development section of the soot sensor element

Photo: staff in charge of the development section of the soot sensor element

“I was thinking for days and days about whether we could do something using the multilayer technology cultivated in the development of ceramic packages. Then my attention was drawn to the soot sensor. In Europe, control of emissions is becoming even stricter, and the present detection system was going to fail the requirement with its current precision. The advantage of multiple layering generally applies to semiconductor components and allows them to be downsized. I came to think that this technique could meet the strict condition of exposure to high temperatures. So we started development in 2013. One of the greatest challenges that we faced in development was the selection of the right materials and determination of the right sintering conditions so that we could successfully sinter ceramic and alloy simultaneously. I hope that successful commercialization of the soot sensor using this element will be able to help not only Europe but also the rest of the world promote application of stricter emissions controls and prevention of air pollution.”

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