Comprehensive realization of the crystal growth perfection of the uni-indexed, bi-indexed and tri-indexed planes of single crystals grown by unidirectional technique- A case study on potassium dihydrogen phosphate

Over the years, even though several research publications have been made on uni-directional crystal growth technique, the plane-dependent crystal growth such as uni-indexed (100), bi-indexed (101) and tri-indexed (111) planes, their crystalline perfection remains to be unclear. On these lines, the present work brings in a possible correlation between them such that it is highly required to extend the applications of the above-mentioned crystal growth technique as well as to understand better the growth kinetics of crystals with respect to their planes. In this work, we have made a systematic comparative analysis of the crystal growth perfection of the uniindexed (200), bi-indexed (101) and tri-indexed (111) planes of potassium dihydrogen phosphate (KDP) single crystals which were grown by unidirectional crystal growth technique known as the SankaranarayananRamasamy (SR) method. For the existing uni-indexed (200), bi-indexed (101) and tri-indexed (332) planes of KDP results, the required data have been procured from the reported results. According to the conventional powder X-ray diffraction (XRD) results, the values of full width at half maximum of the (200), (101) and (332) planes are 0.0402, 0.8656, and 6.016 degrees, respectively. Based on the obtained XRD and high resolution XRay diffraction (HR-XRD) results, it is established that the uni-indexed grown crystals yield a high degree of crystalline perfection while to a certain extent, the bi-indexed crystals, but tri-indexed crystals grow with a lower degree of crystalline nature. Similar types of logical results on crystalline perfection have also been found for the previously reported ammonium dihydrogen phosphate (ADP) and benzophenone single crystals grown by unidirectional crystal growth technique. Analyzing the observed results, uni-indexed crystal planes such as (100), (010), and (001) are more favorable candidates for producing a high degree of crystalline perfection in materials grown by the SR method which are very much required for nonlinear optical applications.