Synthetic sapphire is single‑crystal alumina (Al₂O₃). Its full production workflow includes raw material preparation, crystal growth, ingot post‑treatment, precision machining, surface finishing, coating and inspection. Every step directly determines dislocation density, internal defects, dimensional accuracy and final product performance for substrates, windows, watch crystals, rods and micro‑sapphire parts.

1. Raw Material Preparation High‑purity alumina powder with purity above 99.999% is the base feedstock. Impurities will cause bubbles, inclusions and dislocations inside the crystal. For colored sapphire or ruby, trace dopants such as chromium, iron or titanium are proportionally mixed into alumina powder. Raw materials are purified and dried to remove moisture and foreign particles before loading into the crystal‑growth furnace.

2. Single‑Crystal Growth Several mainstream growth methods are used in industry. The Kyropoulos method is widely adopted for large‑size heavy‑weight sapphire ingots. High‑purity alumina is heated above 2050 °C to fully melt. A seed crystal with fixed crystal orientation touches the melt surface. Through precise temperature‑field control and slow cooling, atoms stack onto the seed, gradually forming a complete large sapphire ingot. Other techniques include Heat Exchanger Method (HEM), Czochralski pulling and EFG edge‑defined film‑fed growth for rods and special profiles. The whole growth cycle can take several days to more than one week.

3. Ingot Annealing & Quality Inspection As‑grown sapphire ingot contains considerable internal thermal stress. Controlled high‑temperature annealing is performed to release residual stress and reduce risk of cracking during subsequent cutting. After annealing, the ingot goes through non‑destructive testing: X‑ray for crystal orientation, infrared scanning to detect bubbles, voids and inclusions. Defective sections are marked and trimmed off. Good‑quality blocks are reserved for further processing.

4. Orientation and Sawing Crystal orientation is critical for downstream performance. According to product requirements (C‑plane, A‑plane, R‑plane etc.), the ingot is oriented by X‑ray diffraction. Then diamond wire‑sawing cuts the big ingot into blanks: blocks, bars, thick slabs or pre‑shaped rough blanks for watch crystals, windows or sapphire rods. Wire‑saw parameters are tightly controlled to minimize kerf loss and surface subsurface damage.

5. Lapping & Grinding Rough‑cut blanks have uneven surfaces and dimensional errors. Double‑sided lapping removes saw marks and achieves target thickness and flatness. For curved parts such as domed pot‑lid watch crystals, CNC form‑grinding generates curved profiles, bevels and edge chamfers. This step brings workpieces close to final geometry, while controlling subsurface damage depth for later polishing.

7. Cleaning and Coating8. Final Metrology and Quality Screening