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钛酸钡陶瓷中，高温下晶格失氧使晶粒内部氧匮乏。在氧化气氛中烧成，晶界则是富氧环境。缺陷或杂 质在晶界上进一步氧化，产生晶粒中并不存在的缺陷种类。杂质和缺陷在晶界上与晶粒内部有不同的行为。某些在 晶界上被氧化成高价态的缺陷和杂质，在晶粒中不能存在，而在晶界上以亚稳态形式存在。它们在铁电相变点跃迁 回低价稳态，产生电子陷阱，使材料电阻率迅速增大，形成ＰＴＣＲ效应。
In barium titanate ceramics, oxygen vacancy is caused by intracrystalline oxygen in the crystal lattice under high temperature. Burning in an oxidizing atmosphere, the grain boundary is oxygen-rich environment. Defects or impurities are further oxidized at the grain boundaries resulting in defect types that do not exist in the grains. Impurities and defects have different behavior from the grain boundaries at grain boundaries. Some of the defects and impurities that are oxidized to the higher valence state at the grain boundaries can not exist in the grains but exist in a metastable state on the grain boundaries. They transition in the ferroelectric phase transition point back to low steady-state, resulting in electronic traps, the material resistivity increased rapidly, the formation of PTCR effect.