铌酸锂晶体的抛光机理及精密加工工艺

POLISHING MECHANISM AND PRECISION MACHINING TECHNOLOGY OF LITHIUM NIOBATE CRYSTAL

采用Stober法制备了平均粒径分别约为50nm和300nm的SiO2抛光液。通过透射电镜、粒径测定仪、zeta电位仪测试和分析了制备的SiO2抛光液的粒径分布、分散度和稳定性。结果表明:抛光液中SiO2溶胶颗粒为球形,溶胶粒子的分散度小,并且具有较好的稳定性。用制备的粒径分别为50nm和300nm的SiO2抛光液对铌酸锂晶体样品进行化学机械抛光,研究了压力、抛光盘速度、抛光液流量及时间对抛光过程的影响。抛光结果表明:采用粒径为50nm的SiO2抛光液的抛光效果最好。最佳抛光工艺参数是:采用沥青抛光盘,50nm的SiO2抛光液,转速为40r/min,抛光液流量为3mL/min,压力为17kPa,抛光时间为60min,去除率为30nm/min。采用激光平面干涉仪、原子力显微镜检测了抛光后样品的面型精度和粗糙度,样品的最佳面型精度为0.134λ(λ=0.6328nm),粗糙度为0.32λ。

Silica dielectric slurries with average particle diameters of about 50 nm and 300 nm respectively can be obtained by the Stober method. The grain size distribution, dispersion degree and the stability of SiO2 colloid slurry were measured and analyzed by transmission electron microscope, particle size apparatus and zeta potentiometer. The results indicate that the particles of silica sol in the silica dielectric slurry are spherical. The dispersion degree of SiO2 colloid particles is poor and the stability of the slurry is good. The chemical mechanical polishing of LiNbO3 crystals was carried out by a large number of experiments using two kinds of silica dielectric slurry. The influence of pressure, polishing plate speed, flow rate of polishing solution, polishing time, and temperature on the polishing quality of LiNbO3 crystal were investigated. The results show that the silica slurry with a particle diameter of 50 nm has the optimal polishing effect, and the optimum parameters were as follows. Polishing should be carried out using an asphalt polishing plate and silica slurry with a particle diameter of 50 nm, a polishing plate speed of 40 r/min, a flow rate of polishing solution of 3 mL/min, a pressure of 17 kPa, a polishing time of 60 min and a polishing removal rate of 30 nm/min. The optimal flatness and surface roughness of samples after polishing were detected by a laser plane interferometer and atomic force microscope. The optimal flatness is 0.134λ（λ=0.6328nm）, and the surface roughness is 0.32λ.