Perovskite oxide of PTCR ceramics as chemical sensors

A new CO gas sensor of perovskite-type oxide, semiconducting La-doped BaTiO3 PTCR ceramics was studied. It is capable of detecting carbon monoxide gas in the concentration range of 1.0% in the high temperature NTCR region near and above the Tmax airP (175–400°C) by means of higher barrier potential of PTCR effect. However, there is only a little resistivity change below the Tmax airP but above the Tc. The phenomenon is based on anionic adsorption, the extreme activity of the oxygen atoms at the grain boundaries, in the higher temperature near and above the Tmax airP The lattice oxygen in the surface layer of the PTCR ceramics participates in the sensing reaction, and the itinerant electron come from the conduction band of the n-type semiconducting ceramics bring about to a decrease in resistivity of the material. A rate of resistivity change of more than one decade on switching the atmosphere from air to 1.0% in low flow rate was observed. We conclude that PTCR ceramics can be used as a new potential CO gas sensor, simple structure, middle/lower operating temperature and low cost, in ceramic chemical sensors development.