LAUSR

ABSTRACT The nano mechanical properties of brittle materials are the key factors affecting nano machining performance. Lithium niobate (LN) single crystal is the typical anisotropic brittle material. The hardness H and crack length of LN crystals on X-cut wafers were measured through indentation experiments, and the fracture toughness KIC and the critical cutting depth dc along <001> orientations were estimated. A set of fixed-abrasive (FA) lapping pads mixed with diamond grains of different sizes were prepared for lapping on X-cut wafers. The effects of abrasive cutting depth δ and dc on material removal rate (MRR) and surface roughness were discussed. Results indicate that: the surface hardness H of X-cut is about 6 GPa. And the minimum KIC and dc on X-cut are 0.67 MPa.m1/2 and 63.6 nm (along <001> orientation), respectively. Lapping tests show that when the abrasive cutting depth δ exceed the dc, MRR will increase significantly, accompanied with brittle material removal and low surface quality.