Industrialization of New PTCR Materials Based on a Ceramics Matrix with a Dispersion of Bi Metal Particles as Ceramic Heaters

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A new type of PTCR materials based on a Bi metal/Ceramics composites has been developed. In this study the possibility for industrialization of the material has been investigated.The composites based on a ceramics matrix with a dispersion of Bi metal particles showed PTCR properties at the melting point of Bi metal of about 270℃. The melting points of temperature were controlled by varying the melting points of Bi alloy particles.The ceramics matrix such as AlィイD22ィエD2OィイD23ィエD2, SrBiィイD24ィエD2TiィイD24ィエD2OィイD215ィエD2 and TiOィイD22ィエD2 have an effect on magnitude of the PTCR properties and a room-temperature resistivity.It was found that the sample 0.76Bi-0.24SrBiィイD24ィエD2(TiィイD20.95ィエD2NbィイD20.05ィエD2)ィイD24ィエD2OィイD215ィエD2 sintered by optimum condition (1125℃, 2h) and by decreasing the particle size of Bi metal to a few micron showed the PTCR property of about 5 orders of magnitude.The relative density of hot-pressed composites with using fine Bi metal reached more than 99% and its resistivity of nearly 10ィイD1-1ィエD1Ωcm at room-temperature unchanged after the cyclic measurement. In addition, the magnitudes of PTCR effect reached 7 order of magnitude, and resistivity-temperature curve also remained unchanged even after 3rd measurements.