Comparative study on L-alaninium maleate single crystal grown by Sankaranarayanan–Ramasamy (SR) method and conventional slow evaporation solution technique Urit Charoen-In a , P. Ramasamy b , P. Manyum a,n a School of Physics, Institute of Science, Suranaree University of Technology, Nakhonratchasima 30000, Thailand b Centre for Crystal Growth, SSN college of Engineering, SSN Nagar 603 110, Tamilnadu, India article info Article history: Received 10 January 2010 Received in revised form 17 May 2010 Accepted 18 May 2010 Communicated by M. Fleck Available online 25 May 2010 Keywords: A1. Directional solidification A1. Etching A1. Optical microscopy A1. X-ray diffraction A2. Growth from solutions abstract Single crystals of L-alaninium maleate (LAM) were successfully grown by Sankaranarayanan– Ramasamy (SR) method and conventional slow evaporation solution technique, which have the sizes of 32 mm in length, 18 mm in diameter and 18  13  2 mm 3 . The grown LAM crystals were subjected to single crystal X-ray diffraction, high resolution X-ray diffraction (HRXRD), chemical etching, dielectric permittivity, dielectric loss, thermo-gravimetric–differential thermal analysis, UV–vis NIR and Vickers microhardness analysis and the results were compared. Single crystal X-ray diffraction confirmed the lattice parameters of the grown LAM crystals. The HRXRD analysis indicated that the crystalline perfection of the SR method grown LAM crystals is quite good without having any internal structural grain boundaries. Chemical etching studies represent the distribution of structural defects in LAM crystal and etch pit density of conventional and SR method grown LAM crystal was calculated. The dielectric permittivity and loss measurement were made as function of temperature in the range 40–140 1C. From thermo-gravimetric–differential thermal analysis of the grown crystal, the thermal stability was found to be up to 158 1C. The range and percentage of optical transmission are represented by recording UV–vis analysis. Mechanical strength of the grown LAM crystals was analyzed by Vickers microhardness test and the hardness of SR method grown LAM crystal is higher than the hardness of the crystal grown by conventional method. & 2010 Elsevier B.V. All rights reserved. 1. Introduction L-alaninium maleate (LAM) is an organic non-hygroscopic material. It has been grown by conventional slow evaporation solution technique (SEST). It belongs to orthorhombic system and the lattice parameters are a ¼5.5873 (11) ˚ A, b ¼7.3864 (17) ˚ A and c ¼ 23.688 (3) ˚ A and the space group is P2 1 2 1 2 1 [1]. There are a few papers reported about the growth of LAM in conventional method including its characterization [2–4]. However the conventional SEST grown crystals have a small size, different morphology, with many faces and poor transparency. For devices we need a large size, defect-free, mechanically and optically good quality single crystals. The crystal with specific orientation can be grown from solution by Sankaranarayanan–Ramasamy (SR) [5] method. This method can be used to grow single crystals along a selected crystal direction, which is very important for the preparation of functional crystals. For example, as the conversion efficiency of SHG is always highest along the phase-match direction for nonlinear optical crystals, the unidirectional crystal growth method is most suitable for the crystal growth along that direction. In addition, the unidirectional solution crystallization usually occurs at around room temperature; much lower thermal stress is expected in these crystals over those grown at high temperatures [6]. From this point of view, we have attempted to grow unidirectional, bulk, good quality single crystals of LAM from its aqueous solution by SR method. In the present investigation, bulk single crystals of LAM were grown by conventional SEST and SR methods. The grown crystals were subjected to various studies in order to determine their properties and the results are compared with one another. 2. Experiments 2.1. Conventional method LAM was synthesized using L-alanine and maleic acid from Merck (GR grade) in the stoichiometric ratio 1:1 with Millipore water of resistivity 18.2 MO cm. The reactants were thoroughly dissolved in Millipore water and stirred well for about 2 h using a ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jcrysgro Journal of Crystal Growth 0022-0248/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2010.05.027 n Corresponding author. Tel.: + 66 4422 4319; fax: + 66 4422 4185. E-mail address: pmanyum@sut.ac.th (P. Manyum). Journal of Crystal Growth 312 (2010) 2369–2375