Semiconducting BaTiO3 ceramics are widely used in electronic information, automatic control, biological technology, energy management and traffic control as an important control component. The barium titanate (BaTiO3) shows high intrinsic resistivity of more than 1010Ω·cm when prepared in the oxidizing atmosphere. Therefore, the chemically unmodified BaTiO3, because of its large energy gap, is an electrical insulator. However, when polycrystalline BaTiO3 ceramics are doped with higher valence cations such as Y3+, La3+, Nb5+ or Ta5+, they show semiconducting properties and positive temperature coefficient of resistance (PTCR) effect.
SiO2 and Mn additions assist homogenization of the microstructure during sintering, improving the performance of PTCR under transient loads. In terms of electrical properties, the variation of permittivity with temperature is significantly affected by SiO2 additions: with increasing SiO2, the permittivity increases below Tc.
SiO2 has long been added to BaTiO3 as a sintering aid, but it has not been reported to significantly affect the electrical properties of PTCR thermistors.
Kong Myong Il, a researcher at the Semiconductor Institute, has investigated the effects of SiO2 addition on PTCR characteristics of Y-doped BaTiO3 ceramics prepared by solid-state reaction method.
He has found through the experiments that the optimum SiO2 content was 2mol.
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