Experimental Research Of KDP Solution Stability And Crystal Growth

The Potassium dihydrogen thophosphate (KDP) crystal was developed since the 40's of the twentieth century; It is one of electro optics and non-linear optical materials and having been broadly applied to some high technology fields such as laser frequency conversion, electro optics modulated, ray celerity switch and so on. It is characterized by very big electro optics, non-linear optical coefficient, high damage threshold, and in particularly, the large-sized single crystal for the ray to get across can be grown. Large-sized KDP crystal is the only material which can be used in ICF (inertial confinement fusion) up till now.With the development of ICF technology, more high-quality and large-sized KDP crystal is in urgent need. Recently, the investigations on KDP crystal growth focus on: improving its growth speed, shortening its growth cycle and reducing its cost in the conditions of maintaining a good crystal quality. Meanwhile, KDP crystal is usually grown by temperature cooling method in solution. The crystal growth process and morphology are easy to be observed. So it is a ideal model for investigating crystal growth. The crystal growth experiments were performed, the main works can be summarized as follows:â‘ The conception and theoretic calculation about metastable zone and solubility of KDP were introduced. The experiments measuring the solubility and metastable zone width were carried out. The solubility curves and the metastable zone width of KDP solution were measured with different pH values. The experiment results were explained by the theory of solution stability.â‘¡The induction period of KDP were determined by the visual method and the effects of temperature and supersaturation on the induction period were observed. The interfacial tension and critical radius of nuclei were calculated basing on the induction period data by using the classical nucleation theory. The crystal growth mechanism was discussed by calculating the surface entropy factor.â‘¢The influence of pH value on KDP crystal growth habits was discussed associated with KDP crystal growth experiments with various pH values. It is found that the higher pH value of KDP solution in comparison with the normal one is more suitable for growing high-quality and large-sized crystal. The pH values of KDP solution in the range of 4.5-5.0 are more proper for KDP crystal growth.