Premium
Compositional dependence of morphology and lattice parameters during growth of K 1‐x (NH 4 ) x H 2 PO 4 mixed crystals
Author(s) -
Srinivasan K.,
Cantoni A.,
Bocelli G.
Publication year - 2010
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.200900656
Subject(s) - tetragonal crystal system , ionic radius , ammonium dihydrogen phosphate , chemistry , composition (language) , crystallography , aqueous solution , phosphate , lattice constant , crystal (programming language) , ion , potassium , analytical chemistry (journal) , ionic bonding , morphology (biology) , crystal growth , crystal structure , diffraction , chromatography , fertilizer , linguistics , philosophy , physics , programming language , organic chemistry , computer science , optics , biology , genetics
Mixed crystals of ammonium dihydrogen phosphate and potassium dihydrogen phosphate K 1‐ x (NH 4 ) x H 2 PO 4 were grown from aqueous solutions with x = 0.06, 0.09, 0.15, 0.32, 0.42, 0.51, 0.63, 0.70, 0.76, 0.78, 0.84, 0.88, 0.89 and 0.91. The crystal composition that differs from solution was estimated by X‐ray method. Morphology of the crystals changes from tetragonal prism to needles when the incorporation of either of the two components into the other; which also affects the growth rate along the prominent growth directions significantly. Growth along the [001] decreases initially with composition and reached the maximum when x = 0.5; whereas growth along the [100] always showed a decreasing trend with composition and attained a minimum value when x = 0.5. Crystal length along the [001] and [100] and aspect ratio are also compositional dependent. Unit cell parameters determined by X‐ray powder and single crystal analyses revealed that the ‘ a ’ parameter shows only a small and linear variation but the ‘ c ’ parameter changes significantly with ADP incorporation because of the difference in the effective ionic radius of K + and NH 4 + ions and also the possibility of NH 4 + ion to form two different kinds of hydrogen bonds in the system. The existence of a pseudo‐cubic cell at the mixing composition x = 0.78 was also revealed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)