A study on development and process optimization of novel eco‑friendly rare‑earth‑based polishing slurry for thin‑walled hard‑brittle curved‑surface quartz crucibles

Thin‑walled hard‑brittle curved‑surface quartz crucibles are critical high‑temperature components for Czochralski monocrystalline silicon growth. Inner‑wall defects such as chipping pits and black spots cause crucible rejection, whereas conventional planar chemical‑mechanical polishing (CMP) fails for curved‑surface defect remediation. Herein, a rare‑earth‑based photocatalysis‑assisted eco‑friendly CMP slurry was developed. Taguchi L25 (5 5 ) orthogonal tests were performed to optimize slurry formulation and processing parameters using areal roughness Sa, signal‑to‑noise ratio and mean roughness as criteria. White‑light interferometry and X‑ray photoelectron spectroscopy (XPS) were employed to characterize surface topography and interfacial chemistry, and crystal‑pulling trials evaluated the service performance of repaired crucibles. The optimal slurry contains 10 vol.% H 2 O 2 , 8 wt.% CeO 2 , pH 9.5, 0.8 wt.% CMC‑Na, 3 wt.% EDTA‑5Na, 3 wt.% TiO 2 and 1 wt.% lanthanum carbonate modifier. Optimal parameters are: normal load 12 N, polishing duration 60 min, illumination intensity 4000 Lux, rotational speed 3000 r/min, slurry flow rate 80 mL/min. Applying this integrated process to 32‑inch spent crucibles eliminates typical inner‑wall defects and yields ultra‑smooth surfaces with Sa 0.724–0.844 nm and seamless substrate‑polished‑zone transition. Comparative pulling tests reveal no statistically significant differences in key crystal‑growth metrics between repaired and brand‑new crucibles. XPS demonstrates that Ce‑based abrasives govern interfacial reactions: photocatalytically generated hydroxyl radicals produce silicate softening layers and surface Si‑OH groups, which condense with abrasive‑bound Ce‑OH to form Ce‑O‑Si bonds removed via mechanical shearing. CMC‑Na suppresses scratches and mitigates heavy‑load damage. This slurry‑photocatalysis synergy enables high‑value‑added remanufacturing of spent quartz crucibles and benefits material‑loss reduction for the photovoltaic silicon chain.