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

The MZ21 PTC Thermistor is a high-performance positive temperature coefficient thermistor designed for reliable overheating protection in electrical applications. With specifications of 400-600 OHMS, 220VAC rating, 160°C operating temperature, and compact 8x2.5mm stone element construction.

PTCR (Positive Temperature Coefficient of Resistance) thermistors feature strong positive temperature characteristics, primarily composed of BaTiO3 ceramic. This ferroelectric material exhibits room temperature resistivity greater than 10¹² Ω·cm, functioning as an insulator. Through semi-conductive doping, it demonstrates a powerful PTC effect with low room temperature resistivity that increases dramatically by several orders of magnitude near the Curie point.

The PTC phenomenon occurs due to barrier layers created by surface states at grain boundaries in polycrystalline BaTiO3 semiconductor material. Below Curie temperature, grain boundaries maintain ferroelectric properties with high dielectric constants and low barrier heights, allowing easy electron passage and low material resistivity. Above Curie temperature, lattice transformation eliminates ferroelectricity, sharply increasing dielectric constants and creating electron barriers that significantly raise material resistivity.