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

Abstract

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° and Y-36° planes were more pronounced than that on X-112° 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°, Y-42°, and Y-36° planes, respectively. The better mechanical properties and “plastic” removal mechanism of X-112° 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° 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.