DEGRADATION BEHAVIOR OF PTCR BATIO3 IN REDUCING GASES

Degradation of positive temperature coefficient of resistivity (PTCR) properties of semiconducting BaTiO3 ceramics that were annealed in red ucing gases was studied from a mechanistic viewpoint mainly by measuri ng the electrical and dielectric properties, using reflectance and ESR spectroscopies, as well as by gas analysis using a quadrupole mass sp ectrometer. The results showed that after annealing, the density of th e surface acceptor states decreased whereas the concentration of condu ction electrons increased. The degradation in PTCR properties was assu med to be caused by the diffusion of hydrogen atoms that were formed f rom reducing gases along the grain boundaries. These atoms reacted wit h chemisorbed oxygen ions, releasing trapped electrons and lowering th e barrier potential.