Solvent effects and polymorphic transformation of organic nonlinear optical crystal L-pyroglutamic acid in solution growth processes : I. Solvent effects and growth morphology

• Published in: Journal of crystal growth Vol. 198; pp. 578 - 582
• Main Authors: Wang, W.S, Aggarwal, M.D, Choi, J, Gebre, T, Shields, Angela D, Penn, Benjamin G, Frazier, Donald O
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1999
• Subjects: L-PGA; L-pyroglutamic acid; Morphology; Solubility curve; Solution growth; Solvent effect; Solvent effect; Solubility curve; L-pyroglutamic acid; 61.66.Hq; 81.20.Ym; Solution growth; Morphology; 81.05.Zx; L-PGA; 81.10.Dn
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/S0022-0248(98)01041-0

Single crystals of a new promising nonlinear optical material for the tunable UV harmonic generation,
l-pyroglutamic acid 60×20×20
mm
3 in size were obtained from aqueous solution by using the temperature-lowering method. Solubility of
l-pyroglutamic acid in different solvents was measured. The single crystals showed different morphological characteristics and growth rate in different solvents with different crystallographic orientations. Methanol or ethanol solutions yielded needle-like crystals. In mixed solution such as methanol/H
2O or ethanol/ H
2O plate-like crystals with a thickness in the direction [0
1
0] were observed. The water as a good solvent, however, produced long prism-like crystals. The two polymorphs of
L-pyroglutamic acid (α and β phases) were found for the first time. The growth shapes of α-phase is mainly a prism and β phases is a rhombic plate.The growth rate of α and β phases is mainly a function of the supersaturation of the
L-pyroglutamic acid in solution.