Perovskite oxide of PTCR ceramics as chemical sensors

Abstract

A new CO gas sensor of perovskite-type oxide, semiconducting La-doped BaTiO 3 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 T max air P (175–400°C) by means of higher barrier potential of PTCR effect. However, there is only a little resistivity change below the T max air P but above the T c. 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 T max air P 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.