The alumina substrates that Ni electrode was printed on and the multi-layered PTCR thermistors of which composition is (Ba_0.998Ce_0.002)TiO_3 + 0.001MnCO_3 + 0.05BN were fabricated by a thick film process, and the effect of re-oxidation temperature on their resistivities and resistance jumps were investigated, respectively. Ni electroded alumina substrate and the multi-layered PTC thermistor were sintered at l,150℃ for 2 h under PO_2= 10^-6 Pa and then re-oxidized at 600∼850℃ for 20 min. With increasing the re-oxidation temperature, the room temperature resistivity increased and the resistance jump (LogR_290/R_25) decreased, which seems to be related to the oxidation of Ni electrode. The small sized chip PTC thermistor such as 2012 and 3216 exhibits a nonlinear and rectifying behavior in I-V curve but the large sized chip PTC thermistor such as 4532 and 6532 shows a linear and ohmic behavior. Also, the small sized chip PTC thermistor such as 2012 and 3216 is more dependent on the re-oxidation temperature and easy to. be oxidized in comparison with the large sized chip PTC thermistor such as 4532 and 6532. So, the re-oxidation conditions of chip PTC thermistor may be determined by considering the chip size.

Citations

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