The role of nonstoichiometry in 180° domain switching of LiNbO3 crystals

Abstract

We show here conclusively that the internal field originates from nonstoichiometric point defects in LiNbO3 crystals. The switching fields required for 180° domain reversal in congruent crystals [C=Li2O/(Li2O+Nb2O5)=0.484] are ∼4–5 times larger than the switching fields for nearstoichiometric crystals (C=0.498). An internal field of ∼2.5 kV/mm observed in congruent crystals disappears in stoichiometric crystals. The concentration of hydrogen incorporated during crystal growth has no effect on the switching or internal fields. The measured spontaneous polarization, Ps=80±5 μC/cm2 is relatively insensitive to the crystal nonstoichiometry and the hydrogen content.