The crystallography and defect chemistry of structural faults in lithium niobate.

Transmission electron microscope studies of Ti-doped, congruent lithium niobate (LiNbO sub 3) have shown that extended structural faults and domain boundaries are only present within the Ti diffused layer (i.e. the wave guiding region). Structural faults have also been observed in undoped Li-deficient LiNbO sub 3, though not in undoped control crystals of congruent and stoichiometric LiNbO sub 3. In both Ti-doped and Li-deficient LiNbO sub 3, crystal chemistry predicts an increase in the concentration of the point defects ''''' over Nb and Nb .. .. over Li. Therefore, it appears that the coalescence of these defects is responsible for the creation of structural faults.