摘要
The bound surface charges generated by the spontaneous polarization of ferroelectric crystals are neutralized by the free charges coming from crystals or the stray charges at constant temperature, so it cannot be detected. The mean time of neutralization by the free charges is τ=ε/σ, where ε is the dielectric constant and σ is the bulk conductivity. The value of τ for the most of pyroelectric materials is about from 1 to 1000 sec. The spontaneous polarization of ferroelectric crystals
