Abstract
BaTiO 3 based PTC thermistors undergo a large and rapid increase in resistance just above the Curie temperature, T C. The resistance increase is predominantly associated with an increase in grain boundary barrier height, therefore it is important to gain information about the grain boundary character in these devices. In this study the microstructures of three different BaTiO 3 PTC thermistor formulations were compared by transmission electron microscopy. The samples differed in the A-site substitutions, giving the formulae: (1) BaTiO 3, (2) (Ba,Ca)TiO 3, (3) (Ba,Ca,Sr,Pb)TiO 3. No grain boundary films were observed, though rounding of the grains at the grain junctions was evidence of a liquid second phase being present during sintering. EDX measurements were made across grain boundaries but no significant segregation of elements to the boundaries was observed.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
