新型有机非线性光学晶体—L-苹果酸脲晶体生长的初步探讨

Investigation on Growth of a New Organic Nonlinear Optical Crystal-Urea L-malic Acid

本文初步探讨了新型非线性光学晶体—L 苹果酸脲的晶体生长 ,研究结果表明 ,L 苹果酸脲晶体在甲醇、乙醇和水三种介质中的溶解度温度系数均较大 ,同温度下L 苹果酸脲晶体在水中的溶解度最大 ,无水甲醇次之 ,无水乙醇中最小。L 苹果酸脲晶体在无水甲醇中的成核自由能比在无水乙醇中的低得多 ,因此在无水甲醇中易于成核 ,晶核数多 ,晶体尺寸小 ,而在无水乙醇介质中 ,虽然成核相对比较困难一些 ,但有利于制备大的单晶 ,且发现低温有利于大晶体的生长。因此宜选择无水乙醇为晶体生长介质。L 苹果酸脲晶体在介质中以非均匀成核方式在试管壁成核长大 ,晶体呈棱柱状 ,生长过程中呈现台阶生长的特征。

The crystal growth of a new organic nonlinear optical crystal-urea L-malic acid (ULMA)-was investigated. The results show that the index of solubility-temperautre of ULMA in water, methanol and alcohol is high so that temperature decreasing method can be chosen to grow the crystal. At the same temperature, the solubility of ULMA is the highest in water, followed by in methanol, and the lowest in alcohol. The nucleation is easy in methanol and the number of nucleation is more,the crystal size is small.While in medium of alcohol, although it is difficult to nucleate, the medium is favorable for preparing large crystals.So alcohol is chosen as the medium of ULMA crystal growth.The nucleation of ULMA is heterogeneous.ULMA crystal is as prism, and its growth seems in accordance with BCF growth theory.