Solution growth and comparative characterization of L‐HFB single crystals

Single crystals of L‐histidine tetrafluoroborate (C₆H₁₀N₃O₂BF_{4 ,} L‐HFB) were grown by solution growth method using two different temperature profiles: conventional, in which the growth temperature was kept constant at 30°C and rapid, in which it was increased in steps of 1 K per day while keeping the other growth conditions same. Crystals grew in nearly 30 and 10 days in the two methods, respectively. The crystals were transparent and showing its characteristic morphology. Both types of crystals were characterized by XRD for their structural comparison. Surface morphology and growth features of the crystals were studied by SEM. Features of two dimensional layer growth steps, rectangular etch pits, slip lines and bands, etc. were observed. The presence of various functional groups and their bonding were studied by FTIR in the range 4000‐400 cm^‐1. Thermal stability of the crystals was determined by thermo‐gravimetric and differential thermal analysis. The generation of green light due to second harmonic generation for fundamental λ =1064 nm has been confirmed in both cases. Dielectric constant measurement was carried out in the range 20Hz‐2MHz. In the UV‐Vis studies, high transmittance and a shorter ‘lower cut off' value (232 nm) were observed. The effect of rapid growth on the structural, morphological and optical properties of the crystals were studied and compared to those of crystals grown in conventional way. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)