Comparative investigations of nonlinear optical (NLO) ammonium D,L-tartrate (AMT) single crystals grown by conventional and unidirectional method

Unidirectional AMT single crystal of diameter 15 mm and length 55 mm was grown with the growth period of 60 days by Sankaranarayanan-Ramasamy (SR) method. The growth conditions have been optimized. A maximum growth rate of 1 mm per day was realized. Employing SEST method AMT crystal of size 12×10×5 mm3 has been grown. The conventional and SR method grown AMT crystals were subjected to TG-DTA, Vickers microhardness, UV-Vis NIR, dark current and photocurrent measurements. TG-DTA evaluated the thermal properties of the grown crystal. AMT was found to be thermally stable up to 206°C. The mechanical behavior of the conventional method grown AMT crystal is affected by the presence of solvent inclusions and it reveals the SR method grown crystal is harder than the AMT crystal grown by conventional method. The SR method grown AMT crystal has 15% higher transmittance as against conventional slow evaporation method grown crystal. The obtained photocurrent value for SR and conventional method grown AMT crystal was 2.6×10−11 amp and 6.7×10−12 amp respectively.