Structure and functional principles of PTC thermistors

  Ceramic materials are commonly used as excellent insulators for high resistance, while ceramic PTC thermistors are manufactured based on barium titanate and doped with other polycrystalline ceramic materials, with lower resistance and semiconductive properties.

  By purposefully doping a material with higher chemical valence as the lattice element of the crystal, a portion of barium ions or titanate ions in the lattice are replaced by higher valence ions, resulting in a certain number of free electrons that generate conductivity.

  The reason for the PTC thermistor effect, which is the step increase in resistance value, is that the material structure is composed of many small microcrystals, which form potential barriers at the grain boundary (grain boundary), hindering electrons from crossing the boundary and entering adjacent regions, resulting in high resistance, This effect is cancelled out at low temperatures: the high dielectric constant and spontaneous polarization intensity at grain boundaries hinder the formation of potential barriers and allow electrons to flow freely at low temperatures. At high temperatures, this effect significantly reduces the dielectric constant and polarization intensity, leading to a significant increase in potential barriers and resistance, exhibiting a strong PTC effect.