Study On High-efficiency Lapping Of Lithium Tantalite Based On Fixed Abrasive Pad

Lithium tantalite（LiTaO₃,hereinafter referred to as LT）is a typical single crystal multifunctional material with excellent piezoelectric,ferroelectric,acousto-optic and electro-optic effects,so it is widely used in narrow-band filters,sensors,photonic tunable filters,acousto-optic devices,gyroscopes,and so on.However,due to the characteristics of low hardness,high brittleness and strong anisotropy,the processing efficiency is relatively low in the conventional free abrasive machining.In order to solve the problems existing in the processing of free abrasive machining,the lithium tantalite wafer was processed by using a fixed abrasive pad.The main research work includes the following aspects:（1）Study on the elastic modulus and hardness of the Y-36°lithium tantalite crystalThe elastic modulus and hardness of Y-36°lithium tantalite wafer were studied by nano-indentation method.When the nano-indentation experiment is carried out,if the loading force is small,the hardness and the elastic modulus test results are easily affected by the surface roughness of the LT wafer and the depth of the indenter into the wafer.Therefore,large load should be chosen in the study of nano-mechanical properties of LT crystal The hardness of Y-36°LT is about 12.6 GPa.When the loading force is 8 to10 mN,the elastic modulus measured and calculated by nano indentation method is stable on Y-36°LT crystal,and the average values are about235.8 GPa,it is less affected by the surface roughness and loading force of the wafer.At the same time,the relationship between the actual machining pressure and the elastic modulus of LT is analyzed.（2）The manufacture of fixed abrasive padThe design and manufacturing of the fixed abrasive pad,the design of formula,including the structure,manufacturing process and trimming process are researched,and a high machining efficiency and good quality fixed abrasive pad is designed,which were tested and analyzed for the physical properties,it is trimmed and machined.（3）Lapping lithium tantalite wafer by using fixed abrasive padThe effects of abrasive type and abrasive size on the surface roughness and material removal rate of lithium tantalum crystal were analyzed by single factor experiment.The results showed that the lapping effect of diamond abrasive on lithium tantalum wafer was better than that of silicon dioxide abrasive,the abrasive size smaller,the lapping quality better,the material removal rate smaller.The surface morphology,surface roughness and material removal rate of lithium tantalite wafer were compared between free abrasive and fixed abrasive pad,and the lapping effect of fixed abrasive pad was better than free abrasive.The critical conditions of the spherical abrasive particles embedded in the workpiece in the free abrasive machining process are analyzed,and the connection between the abrasive and the workpiece in the fixed abrasive pad machining process is also analyzed.（4）Study on process optimization of lapping lithium tantalite wafer by using fixed abrasive padThe effects of various parameters（lapping pressure,rotational speed,hydrogen peroxide concentration）on the surface roughness and material removal rate of lithium tantalite wafer were studied by orthogonal experiment.The surface roughness of the lithium tantalite wafer becomes smaller as the lapping pressure increases.At the same time,as the rotational speed of the lapping pad increases,the surface roughness of the lithium tantalite wafer becomes larger as the concentration of hydrogen peroxide increases.The material removal rate of the lithium tantalite increases with the increase of the lapping pressure,increases with the increase of the lapping pad rotation speed,and increases with the increase of the hydrogen peroxide concentration.Considering the material removal rate and surface roughness of lithium tantalite wafer,the optimum technological parameters are as follows.Lapping pressure is 4 kPa,the rotational speed is 120r/min,hydrogen peroxide concentration is 0%.Under this condition,the material removal rate of lithium tantalite wafer is 64.34μm/h and the surface roughness S_a is 38 nm.