Lithium niobate crystal, abbreviated as LN, belongs to the tripartite crystal system and has an ilmenite type (distorted perovskite type) structure. Relative density 4.30, lattice constant a=0.5147 nm, c=1.3856 nm, melting point 1240 ℃, Mohs hardness 5, refractive index n0=2.297, ne=2.208（ λ= 600 nm), dielectric constant ε= 44, ε= 29.5, ε= 84, ε= 30, primary electro-optic coefficient γ 13= γ 23=10 × 10pm/V, γ 33=32 × 10pm/V Γ 22=- γ 12=- γ 61=6.8 × 10pm/V, nonlinear coefficient d31=-6.3 × 1p0 m/V, d22=+3.6 × 10pm/V, d33=-47 × 10pm/V. Lithium niobate is a ferroelectric crystal with a Curie point of 1140 ℃ and a spontaneous polarization strength of 50 × 10C/cm '. The deformed lithium niobate crystal has multiple performance materials such as piezoelectric, ferroelectric, optoelectronic, nonlinear optical, thermoelectric, etc., and also has photorefractive effect.