A novel approach of precision polishing for KDP crystal based on the reversal growth property

A novel approach of precision polishing based on the reversal growth property is proposed for potassium dihydrogen phosphate (KDP) crystal. The approach utilizes the unsaturated growth solution of KDP crystal to polish the crystal itself. The reversal growth property and its influence factors are studied. For this precision polishing approach, the mechanism of surface planarization is analyzed. Some preliminary investigations on the surface planarization performance are also carried out. Results show that the reversal growth property of the KDP crystal is closely related to the characteristic of KDP solution, namely, temperature, concentration, and flowability. With the appropriate coordination of these factors, the reversal growth of KDP crystal can be achieved under a highly controlled manner. By using this novel polishing approach, the macrostructures on the KDP crystal workblank can be removed efficiently. Additionally, through a multiple-stage polishing process, the surface rms roughness of the KDP crystal declines from 5702.4 nm to 17.1 nm in 2 min, meanwhile, the average material removal rate is 51.7 μm/min.