The pH effects on the growth rate of KDP (KH2PO4) crystal by investigating Raman active lattice modes

We report on the dependence of the pH value on the growth rates of KDP single crystals. Extensive experimental work has been carried out in order to find the optimum pH ranges for growing KDP single crystals with suitable sizes and high optical quality. Different techniques including micro-Raman back-scattering spectroscopy, UV/vis/IR transmission spectroscopy and X-ray diffraction have been employed for this investigation. Deuterated substituted single crystals of KDP and DKDP also have been grown for the investigation of growth rates and Raman active mode identification purposes. The molecular vibration modes of the grown crystals, including internal modes Of PO4 tetrahedrons molecular vibrations, external modes of optical phonons and hydrogen bonding modes have been determined exactly by micro-Raman back-scattering spectroscopy. The best pH values of the solution for the KDP crystal growth with reasonably higher growth rates from. aqueous solutions that have been supersaturated ata temperature range of 30-50 degrees C have been found to be in the pH range of 3.2-5.4. Copyright (C) 2007 John Wiley & Sons, Ltd.