Point Defects in Lithium Niobate Single Crystals Used in Laser Modulation

摘要

The electrical conductivity of single crystal lithium niobate (LiNbO3) was determined as a function of temperature for various oxygen partial pressures. The electrical conductivity is proportional to (P sub O2) to the -1/4th power which can be explained by a defect equilibrium involving singly ionized oxygen vacancies and electrons. Thermoelectric measurements indicate that LiNbO3 at low oxygen partial pressures is n-type. Measurements of electrical transport numbers at 1000K show the electrical conductivity of LiNbO3 to be ionic at one atmosphere of oxygen and electronic at low oxygen partial pressures. The diffusion of oxygen in LiNbO3 was determined as a function of temperature at an oxygen partial pressure of 70 Torr by measuring O18/O16 isotope exchange with the gas phase as a function of time. Consideration of the Nernst-Einstein relation for oxygen and the variation in conductivity with Li2O activity indicate that the ionic conduction is caused by transport of lithium ions. (Author)