Crystallographic orientation effect on the polishing behavior of LiTaO3 single crystal and its correlation with strain rate sensitivity

Lithium tantalite (LiTaO3 or LT) single crystal has been extensively applied in the fields of electro-optical and piezoelectric devices. As a typical anisotropic material, the crystallographic orientation effect on its machining responses, i.e., surface roughness and material removal rate (MRR), is not yet well understood. In the present work, we investigated the polishing responses of the three typical crystallographic orientations for LT single crystal under a series of rotation speeds. The results showed that both the rotation speed and crystalline orientation had little effect on the quality of polished surface. While for the MRR, it was almost linearly increased with increasing rotation speed for all of the three planes, among which the enhancements of MRR on Y-42 degrees and Y-36 degrees planes were more pronounced than that on X-112 degrees plane. The scratch features and friction coefficients were investigated using a nanoindentation system under various velocities. The nano-hardness values were obtained under various strain rates and, hence, the strain rate sensitivities (SRS) were determined as 0.0172, 0.0455, and 0.043 for X-112 degrees, Y-42 degrees, and Y-36 degrees planes, respectively. The better mechanical properties and plastic removal mechanism of X-112 degrees plane resulted in the lower value of MRR. Also, the much lower SRS corresponded well with the relatively less sensitivity of MRR with rotation speed on X-112 degrees plane. Results of this study suggested that the plastic parameter of SRS could provide as an excellent indicator to bridge the machining response and intrinsic deformation mechanism for brittle single crystal ceramics.

Automated summary

This study investigated the relationship between the polishing responses of lithium tantalite single crystal and its crystallographic orientation and rotation speed. The results showed that crystallographic orientation had little effect on surface quality, but rotation speed had a linearly increasing effect on material removal rate (MRR). The study also found that the X-112 degrees plane had better mechanical properties and a lower MRR value due to its plastic removal mechanism.