Study of PTC effect in BaTiO3 ceramics

The PTC effect has been found in certain semiconducting ferroelectric titan ate ceramics and is directly related to the interaction between the grain b oundary electronic acceptor states and the ferroelectric-paraelectric phase transition ata the Curie temperature. This effect has been characterized b y an anomalous rise in resistivity of several orders. Perovskite type BaTiO 3 pellets have been prepared by using standard ceramic route. The starting materials are commercial grade barium carbonate and titanium dioxide. The p ellets are finally sintered in air at 1400 degreesC for 1 hr. The silver el ectrodes ar formed on both sides of the pellets by vacuum evaporation. The de resistivity measurements have been done by applying 1 volt de across the sample and measuring the current through 610C. Keithley electrometer at va rious temperatures. Four order change in resistivity has been observed abov e the Curie temperature. The phase confirmation has been made by X-ray diff ractometry (XRD). The microstructure of the material has been examined by s canning electron microscopy (SEM).