一、引言在温度恒定的条件下,铁电晶体的自发极化强度引起的面束缚电荷被晶体内部和外来的自由电荷所中和,因此觉察不出来,晶体内部自由电荷起中和作用的平均时间为τ=ε/σ,其中ε为晶体的体介电常数,σ为晶体的体电导率。多数铁电晶体的τ值在1秒到1000秒之间。铁电晶体的自发极化强度通常随温度的增加而减小,所以当晶体的温度变化率大于τ~(-1) I. INTRODUCTION Under the condition of constant temperature, the surface bound charges caused by the spontaneous polarization of ferroelectric crystals are neutralized by the free charges inside and outside the crystal. Therefore, it can not be observed that the average charge of the neutral charges in the crystal interior Time is τ = ε / σ, where ε is the bulk permittivity of the crystal and σ is the bulk conductivity of the crystal. The τ value of most ferroelectric crystals is between 1 second and 1000 seconds. The spontaneous polarization of ferroelectric crystals usually decreases with increasing temperature, so when the temperature change rate of the crystal is more than τ ~ (-1)