Nowadays, optical and laser devices are constantly evolving [1–3], the demand for the fabrication of functional materials in this field is increasing, in which Y3Al5O12 material has outstanding properties such as good optical properties, high thermal conductivity along with combinations of excellent rare earth ionic [4–6]. However, with difficult-to-machine properties such as high brittleness and hardness, it is difficult to achieve ultra-precise surface quality, with low surface quality that will reduce the efficiency of the laser, due to the low-quality surface will cause local energy accumulation for laser scattering [7–9]. In addition, the cost of the Y3Al5O12 material processing process also increases significantly due to its chemically stable nature thereby making the residual material removal rate low.
In recent years various ultra-precision machining methods have been used to produce ultra-fine Y3Al5O12 workpiece surfaces. The main methods used include chemical, magnetorheological finishing, mechanical, and chemical mechanical slurry (CMS) polishing [10, 11]. When mechanical and magnetorheological polishing for Y3Al5O12 material, it is necessary to use abrasive particles with a higher hardness than Y3Al5O12, in this case, scratches appear along with which the Y3Al5O12 workpiece surfaces are easily displaced and appear large protrusions after polishing [12, 13]. Meanwhile, chemical polishing processes with Y3Al5O12 material by phosphoric acid at high temperature and concentration will adversely affect the environment and equipment, in addition, create corrosion pits on the surface after polishing along with the ability to remove residuals on the surface of uneven workpieces . These characteristics suggest that mechanical or chemical polishing alone is not suitable for polishing Y3Al5O12 material. Studies by Wang et al.  show that when combined mechanical and chemical action in polishing processes can produce high surface quality by soft abrasive particles. In the process of polishing by CMS, the composition of the CMS has a great influence on the cost and surface quality, the current studies mainly focus on polishing Y3Al5O12 material by colloidal silica. Y3Al5O12 material surfaces can be made in nanometer form when polished by chemical cloth and colloidal silica. The studies by Li et al.  showed that the surface of Y3Al5O12 material was significantly improved when polishing by CMS containing a mixture of SiO2 and NaOH suspensions, but the removal capacity of the workpiece residue was low 0.29 (nm/min). Besides, another factor affecting the use of colloidal silica is that the ability to remove the processing residue is reduced in the process of reusing colloidal silica to produce –Si–OH [17–19]. Several studies have been conducted to improve the performance of colloidal silica, however, the performance improvement is still limited . As such, there are still many problems to be solved in CMS polishing for Y3Al5O12, which necessitates the creation of a new CMS blend for efficient material removal and improved surface quality better.
The polishing process uses a mixture of colloidal silica, mechanical polishing processes and chemical reactions are grouped together because the –Si–OH produced are distributed on the surface of the silica particles as a reactant. With this feature, the polishing process performance is degraded because there is unbalance between chemical and mechanical polishing effects, therefore need to generate the Si-OH group in ionic form instead of solid form on abrasive particles. This process is solved by Na2SiO3 solution, in which Si-OH groups are generated by hydrolysis of SiO32− . In this work, the –Si–OH components are separated from the abrasive particles created by the Na2SiO3-5H2O solution along with the mechanical process performed by the ZrO2 abrasive. Besides that, the polishing processes by CMS are added with MgO to improve the ability to material remove as well as further improve the surface quality. Experimental processes have been performed showing that CMS containing percentage composition of Na2SiO3-5H2O, ZrO2, and MgO of 5%, 8%, and 1%, respectively, gives the highest polishing efficiency of Y3Al5O12 material.