BULK AND SURFACE RESISTIVITY OF LINBO3 AND LITAO3 CRYSTALS VERSUS TEMPERATURE

Adopting a specially designed circuit with a lock-in amplifier we succ essfully 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 detec ted experimentally. With such new technique we measure the bulk and su rface resistivity of single domain z-cut polarized and c-cut unpolariz ed 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 c urrent and temperature so established confirms the presence of two mec hanisms of conduction in c-cut unpolarized and z-cut polarized LN and LT, namely, band conduction and hopping conduction on small polarons a nd gives their transition temperatures T(t). Certain anomalies emergin g in the application of LN and LT have been interpreted from the viewp oint of further analysis.