Effect Of Nano/micron Particles On The Properties Of PTCR Semiconducting Materials

The scientific value and application foreground of nano-technique and nano-material is already known to mankind. Nano-technique and nano-material have been taken for one of three fields of science and technology in the 21st century. Its application in material research has broadened the view of preparation of materials with high performance.PTCR (positive temperature coefficient of resistance) is a type of temperature sensitive material which possesses positive temperature coefficient. In recent years, with the development of electronic ceramic materials, nano-technology has been already introduced into the preparation of PTCR materials to obtain high performance posistors. More and more researchers pay attention to this direction. The researches are mainly focused on super fine powders with high purity via sol-gel process, co-precipitation and hydrothermal methods in order to improve the performance of PTCR. Considerable progress has been achieved in the field over last decades. However, as the performance of PTC materials is improving, the cost of production is growing higher and higher.On the other hand, the semiconducting additives, Nb₂O₅ and Y₂O₃, sintering and modifying additives, Al₂O₃, SiO₂, Li₂CO₃, Sb₂O₃ and BN, are added on very small scale, but they play a crucial role in the fabrication of PTCR materials. However, the research on these key additives of PTCR is little reported.This paper is devoted to further enhance the properties of PTCR materials through small amount addition of several additives with nano or submicron particle size, including Al₂O₃, SiO₂, TiO₂ and BN, in order to reduce the production cost compared with current way of using nano powders as main starting materials.In the second chapter, the effect of nano-particles of Al₂O₃, SiO₂ and TiO₂ on the properties of PTCR materials is investigated. The experiment results show that the addition of nano-particles improves the properties of PTC ceramics remarkable. When nano-particles of SiO₂, Al₂O₃ and TiO₂ (additive amount: 0.55 mol.%, 0.22 mol.%, 0.5 mol.%) are added, the room-temperature resistivity can be decreased by 57.9%, jumping increased by a magnitude of...