Crystalline perfection and optical properties of rapid grown KH_2PO_4 crystal with chromate additive

摘要

Potassium dihydrogen phosphate (KDP) crystals were grown in the presence of a series of chromate (CrO_4~(2-)) additive concentrations via rapid growth method. CrO_4~(2-) made KDP crystals were coloured by yellow-green, suggesting CrO_4~(2-) had entered into the crystal lattice. The elemental analysis indicated that Cr element in KDP crystal was at ppm level. High resolution X-ray diffraction data revealed that the crystalline perfection of these as-grown KDP crystals was destroyed after CrO_4~(2-)entered into crystal lattice, embedded in the full width at half maximum was broadened and satellite peaks appeared. Additionally, the extinction ratio was decreased with rise of CrO_4~(2-) concentration. CrO_4~(2-) introduced two absorption peaks centred at 360 and 280 nm and enhanced the intrinsic absorption near 220 nm, which were at the same band positions compared with the CrO_4~(2-) or HCrO_4~-transmittance spectra. Additionally, CrO_4~(2-) could increase the size of light scattering, which was attributed to the point defects and microscopic defects by the replacement by CrO_4~(2-) at PO_4~(3-) position.