Abstract
A new type of PTC material based on Bi metal/ceramics composites has been developed. Bi/SrBi 4 (Ti 0.95 Nb 0.05 )O 15 composites with various Bi contents were fabricated by powder metallurgical process. It was found that the samples of x= 0.73∼0.80 in xBi-(1-x)SrBi 4 (Ti 0.95 Nb 0.05 ) 4 O 15 composites fired at 1075°C for 2 h in Ar atmosphere can show the PTCR properties at the melting point of Bi metal of about 270°C. The composites consisted of the microstructures where Bi metal phases were dispersed in the SrBi 4 (Ti 0.95 Nb 0.05 ) 4 O 15 ceramics matrix. The same techniques were applied to other ceramics matrix. Both of Bi/TiO 2 and Bi/A1 2 O 3 composites were confirmed to show PTCR properties at the same temperature. Since the resistivity-temperature characteristics at higher temperatures were determined by the ceramic matrix, the resistivity of composites and the magnitudes of PTCR effect could be controlled by choosing the different resistivity of the ceramic matrix.
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