Single-crystal growth of 4-hydroxy-3-methoxy benzaldehyde by the Bridgman technique and its characterization

Single‐crystal growth of 4‐hydroxy‐3‐methoxy benzaldehyde (vanillin), an excellent molecular nonlinear optical (NLO) material, from the melt using the Bridgman technique is reported for the first time. Differential thermal analysis experiments indicated that the substance melts congruently at 81 °C. A precise temperature profile plot of the resistive furnace used was measured using a simple PC‐based time–temperature data logging system. Powder X‐ray diffraction analysis of the grown crystal revealed the crystal belongs to the monoclinic system. Fourier transform infrared spectra were used to assign various modes and identify the functional groups. The crystal exhibited a wide window of transmission unlike other organic NLO crystals. The optical second harmonic generation conversion efficiency of vanillin was determined using the Kurtz powder technique. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)