Design, Preparation and Properties of Zr/Ce Oxide Powders for Application in Oxygen Gas Sensors

• Main Authors: Kai-Hsin Chang, 張凱昕
• Other Authors: Chin-yi Chen
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/12666600064321406986

碩士 === 逢甲大學 === 材料科學所 === 99 === In this study, nanocrystalline zirconia-added ceria powder was prepared from cerium nitrate hydrate (CeNH) and zirconium nitrate hydrate (ZrNH) by precipitation method. Zirconia with various additions, 0, 5, 10, and 15 at.%, was added into ceria as CeO2, 5ZDC, 10ZDC and 5ZDC. The modification of the oxygen sensing characteristics of ceria powder was investigated. The influence of different amounts of zirconium ion additions on the electric conductivity, oxygen sensing behavior, and activation energy of electric resistance of ceria coating as a function of temperature was discussed. The experimental results were then applied to a temperature-independent oxygen sensor device in the final part of the study. The experimental results indicated that the ceria powder obtained from precipitation showed an irregular shape with a good crytallinity. The crystallite size was ca. 6 to 7 nm. After heat-treating the powder at 900C and 1200C, zirconia could inhibit the growth of CeO2 crystals significantly and reduce the lattice constant of ceria, shortening the hopping distance of ions. In the mean time, the amount of Ce4+ reacted to Ce3+ was enhanced to cause the increase of electric conductivity of the composite. Ceria powders were then prepared as a resistive oxygen sensor by screen printing technique where the 10ZDC exhibited better electric resistance reduction and oxygen sensing kinetics in this system. The experimental result showed that the connection and porosity influence significantly the electric conduction and gas sensing behavior of the powder coatings. According to the calculation of the activation energy from the temperature vs. electric resistance plots, respective the 5ZDC and the 10ZDC were used as temperature compensating material (TCM) and oxygen partial pressure measurement material (OMM) for the fabrication of resistive oxygen sensor which would not be affected by temperature change. The results showed that the device exhibited excellent temperature-independence and oxygen sensing behaviors.