Influence of MoO₄2- on crystalline perfection and optical properties of potassium dihydrogen phosphate (KDP) crystal

摘要

A series of KDP crystals are grown by rapid growth method by altering the concentrations of the MoO₄2- in the range from 0 to 500 ppm (mol ratio). The growth habits of the KDP crystals suggest that MoO₄2- possess the similar effect with metallic cations, which can inhibit the growth of prismatic faces of KDP crystal. Lower concentrations of MoO₄2- could induce liquid inclusions in the prismatic sector. The liquid inclusions overlapped with each other. However, higher concentrations of MoO₄2- can cause detached rod-like liquid inclusions in the pyramidal sector. With a rise of MoO₄2- concentration, the static extinction ratio of KDP crystals decreased, and the full width at half maximum of the rocking curves is broadened. MoO₄2- enhanced the transmittance in the range of 200-400 nm for prismatic sector, which is attributed to that MoO₄2- is prone to be absorbed onto (100) face, and consequently blocked and the entrance probability of metallic cations into KDP crystal. The conoscopic interference indicates the optical homogeneity of KDP crystal is spoiled by MoO₄2-. Additionally, MoO₄2- can increase the density of light scatters and the size of single light scatter.