Investigation On The Growth Characteristics Of ADP Single Crystal And Thin Surface Layer

As an inorganic nonlinear optical material with excellent optical properties, ADP single crystal with high quality and ample size holds an important position on laser and photoelectron technology applications. ADP crystal is an important member of KDP-type crystal, recent research indicated that ADP crystal could changed from ferroelectric to antiferroelectric under certain conditions, which made ADP crystal more important among KDP-type crystal, and the demand for ADP crystal also increased quickly. Grown from solution was the most commonly used method of making ample size ADP crystals, and the growth of thin surface layerswas one of the strange phenomena during ADP crystal grow from solution. Unlike normal crystal growth, thin surface layers grew hanging in ADP solution, without crystal structures under them as crystalline basement. The regeneration of Z-cut plate seeds was the typical phenomenon of the growth of thin surface layers, and the final formation of crystalline cone was a ‘box-like' structure formed by thin surface layers with solution in it. As we all know, Z-cut plate seeds were the most widely used seeds in growing large scale KDP-type crystals currently. Many studies showed that, the regeneration of Z-cut plate was an very important process during the growth of crystal, which would influence crystal quality and final utilization significantly. Besides, some researchers found that the crystal had incomplete shape could also regenerated to it's ideal shape by thin surface layers, but the growth of thin surface layers would form many liquid inclusions, which were serious defects of single crystal. Nowadays, there still had no reasonable explanation about the growth mechanism of thin surface layers, it's meaningful to make studies about the growth characteristics of thin surface layers.In this paper, The influence of different type ADP crystal samples, which could be obtained by diamond wire cutting machine, on the formation and growth characteristics of thin surface layers of ADP crystal was experimentally analyzed, and also discussed from the view of growth kinetics.The main contents can be summarized as following:(1) The solubility curve of ADP solution were measured by experiments, which laid the foundation for the growth of ADP single crystal and thin surface layers experiments.(2) Experiments were designed to grow ADP single crystal by ‘point seed' crystal growth method. Two different type point seeds obtained by ‘nature evaporation method' and ‘diamond wire cutting method' were introduced, and the advantage and disadvantage of growing ADP crystal by these two type point seeds were also discussed.(3) The influence of concave angles on the growth characteristics of thin surface layers of ADP crystal was analyzed. The growth phenomena of five different type samples, which obtained by diamond wire cutting machine, were observed to comparative analysis the growth characteristics of thin surface layers. The results showed that the orientation of concave angles have significant influence on the growth of thin surface layers and under certain conditions, thin surface layers were most easily formed at concave angles.(4) The formation and growth characteristics of ADP crystal with different edge angles were observed, and combined with microscopic in-suit observation, the influence of edge angle on the growth of thin surface layer was analyzed. It was found that if the normal angles were destroyed, the shape judgement of ADP crystal and the growth rate of thin surface layers would be significantly affected. The microscopic in-suit observation consequences showed that edge angles might be the main source of thin surface layers. Besides, the thickness of thin surface layer was also measured by microscopic in-suit observation system.(5) Microscopic in-suit observation system was designed to research the kinetics of thin surface layers. The rules of the tangential growth rate of thin surface layers versus phase transition drive force was obtained and discussed. Besides, the growth rate of thin surface layers at different angle types were obtained by in-suit recording the advancement of the leading edges of thin surface layers and corresponding growth kinetics coefficients were calculated. The influence of edge angle on the growth of thin surface layers was quantitative analyzed.