The influence of CeO2 abrasive size on the performance of photocatalytic assisted chemical-mechanical polishing by Y/Pr co-doping strategy

Abstract

The synergistic effect of photochemical oxidation activity and tribochemical ability of CeO2 material is a necessary prerequisite for the formation of photocatalytic assisted chemical-mechanical polishing (PCMP) abrasive system. However, it is precisely due to the large band gap (∼ 3.2 eV) of CeO2 and the high recombination rate of photogenerated carriers that the improvement of the photocatalytic oxidation activity of traditional CeO2 photocatalysts is greatly limited, thus preventing the further wide application of cerium-based abrasives in PCMP. Based on this, a series of Ce1–2xYxPrxO2 abrasives were synthesized by molten salt method to improve the performance of cerium oxide based polishing paste with PCMP. The physicochemical properties of Ce1–2xYxPrxO2 samples were analyzed by a series of characterization methods. The results show that Ce1–2xYxPrxO2 abrasive has a normal octahedral shape with a particle size of 190 ∼ 260 nm. With the increase of doping amount, the particle size of abrasive decreases gradually, but the photocatalytic activity increases. Compared with undoped CeO2 abrasives, the removal rate (RR = 932.42 nm/min) of quartz glass by Ce1–2xYxPrxO2 abrasive was increased by about 87.10%. At the same time, the surface quality has been significantly improved. A smooth, flawless and low roughness surface was obtained. The improvement in surface quality can be demonstrated by reducing surface roughness (Ra). The Ra of quartz glass decreased to 0.36 nm after Y3+/Pr3+ co-doped CeO2 abrasive by PCMP (the original Ra of glass was 1.08 nm). It was considered that the size of the abrasive had a close relationship with the surface quality and the RR of the polished glass. Meanwhile, characteristic co-doping strategy was conducive to increase the Ce3+ and oxygen vacancy concentration of CeO2 particles, which optimized the separation efficiency of the photogenic carrier of the photocatalyst. This further promoted the generation of oxidizing active substances in the polishing slurry, and therefore expediting the formation and removal of the chemical reaction soft layer. The removal mechanism of Ce1–2xYxPrxO2 abrasives in PCMP process was discussed.