BULK AND SURFACE RESISTIVITY OF LINBO3 AND LITAO3 CRYSTALS VERSUS TEMPERATURE

Adopting a specially designed circuit with a lock-in amplifier we successfully eliminate the pyroelectric and other disturbances in LiNbO3 (LN) and LiTaO3 (LT) crystals, which have so far prevented the role of their characteristic resistivities versus temperature from being detected experimentally. With such new technique we measure the bulk and surface resistivity of single domain z-cut polarized and c-cut unpolarized LN and LT single crystals at temperatures between 0 and 150-degrees-C and in some cases from -32 to 180-degrees-C. The relation between current and temperature so established confirms the presence of two mechanisms of conduction in c-cut unpolarized and z-cut polarized LN and LT, namely, band conduction and hopping conduction on small polarons and gives their transition temperatures T(t). Certain anomalies emerging in the application of LN and LT have been interpreted from the viewpoint of further analysis.