Charge Transfer in Polar Crystals

In some noncentrosymmetric crystals, their internal polarity can significantly influence the electric charge transfer. Sometimes, mixed ion-covalent bonds that are intrinsic to polar crystals are extremely delicately balanced, therefore, external stimuli (temperature or electric field) lead to a large change of the specific electrical resistance. In this case, even a small violation in the structure of materials stipulates a significant influence on electrical resistance, namely, a strong temperature dependence of the specific resistance of critistors and posistors and also field dependence of the specific resistance in varistors and controlled switching elements. A high sensitivity of specific resistance to peculiarities of the external environment that is stipulated by the imbalance of the internal polarity of active material is used in sensors. The analysis of the influence on electric charge transfer in polar structures can be crucial for the improvement of appropriate materials.