Resistive Oxygen Gas Sensors Using Cerium Oxide Nanosized Powder

摘要

Cerium oxide nanosized powder was synthesized by modified precipitation method. The precipitate, which was formed from the addition of NH_4OH to Ce(NO_3)_3 aqueous solution, and was filtered. The obtained gel was mixed with carbon powder with a particle size of about 20 nm by a mechanically rotating mixer. The mixture was dried at 343 K in air. The carbon powder was burned out by heat treatment at 1173 K in air for 4 h, resulting in the formation of CeO_2 powder with a size of 50 nm. A thick film was formed on an alumina substrate by screen printing, and was fired at 1373 K. The thick film had porous structure and the grain size was about 120 nm. The resistance of the thick film was almost proportional to P(O_2)~(1/6), where P(O_2) is oxygen partial pressure, in the P(O_2) range from 10~(-13) to 10~5 Pa at 1073 and 1173 K. The response time (t_(90)) was 23 and 7 ms at 1023 K when P(O_2) changed from 65 to 25 kPa and 25 to 65 kPa, respectively. The reason for this result was explained on the basis of surface reaction of cerium oxide grain.