MZ21 PTC Thermistor 400~600 OHMS 220VAC 160C 8x2.5mm Stone Element for Over Heating Protection

PTCR (Positive Temperature Coefficient of Resistance) is the 1 kind of thermistor with strong positive temperature characteristics, mainly composed of BaTiO3,BaTiO3 ceramic is the 1 kind of typical ferroelectric material, room temperature resistivity is greater than 10 12 Ω cm, for insulator, after semi-conductive doping shows a strong PTC effect-room temperature resistivity is very low, with the increase of temperature, in the vicinity of the Curie point mutation, resulting in several orders of magnitude of change. This is because there is a barrier layer caused by surface states at the grain boundary of polycrystalline BaTiO3 semiconductor material. At Curie temperature, the grain boundary has ferroelectricity, the dielectric constant is very large, the barrier height is low, electrons can easily pass through the barrier, and the corresponding material resistivity is small.