Near-Electrode Processes in LiNbO3 Crystals with Different Domain Structures

The influence of conductive coating materials on the magnitude of short-circuit currents (SCC) in single-domain and polydomain Z-cut polar lithium niobate (LiNbO3) crystals is investigated. The domain structure of the samples was determined by piezoresponse force microscopy (PFM) using a probe microscope. Indium and silver symmetrical (identical) coatings were used for the study. Temperature dependences of SCC were measured using a hardware complex with special software in the temperature range from room to 350°C at a rate of 2 deg/min in air without applying an external electric field. Even at room temperature the SCC are observed on all investigated samples. The direction of the SCC flow depends on the conductive coating material, and the domain structure influences the current magnitude during heating. The current flow was in the positive direction for In conductive coatings and in the negative direction for Ag conductive coatings. In the single-domain samples observed higher currents than those in polydomain ones. The surface of the conductive coatings before and after heating was investigated using an optical microscope. Significant changes in the structure and color of the conductive coatings are observed. The obtained data demonstrate a significant dependence of SCC on the type of domain structure and the material of conductive coatings, which is important to consider when developing stable piezoelectric devices operating in a wide temperature range.