International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Special Issue: 09 | Sep -2017 www.irjet.net p-ISSN: 2395-0072 One Day International Seminar on Materials Science & Technology (ISMST 2017) 4 th August 2017 Organized by Department of Physics, Mother Teresa Women’s University, Kodaikanal, Tamilnadu, India © 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 393 Mechanical and dielectric nature of organic molecular anthracene single crystal R. Ragu 1 , M. Akilan 1 , A. Sybil Emarance 1 , S. Jerome Das 1* 1 Department of Physics, Loyola College, Chennai 600034, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - High quality anthracene single crystals which is used as model organic molecular crystal used in the studies of solid-state properties has been grown by solvent evaporation method. The unit cell parameters of the grown crystals have been studied by single crystal X-ray diffraction analysis. Vicker’s microhardness studies is carried out to investigate the mechanical properties like fracture toughness, brittleness index and elastic stiffness constant. Dielectric behaviour is studied for different frequency at various temperature and the results were discussed Key Words: Crystal growth, Single crystal X-ray diffraction, Mechanical, Dielectric studies 1. INTRODUCTION Ramesh Babu et al. [1] reported that organic crystals shows remarkable opto-electronic properties due to delocalized electrons namely conjugated electron system possess various photoresponses such as photoconductive, photovoltaic and so on. Madhurambal et al., has already grown anthracene single crystals by using slow evaporation technique with various solvents namely acetone (C3H6O), benzene (C6H6), carbon tetrachloride (CCl4), carbon bisulfide (CS2) [2-3]. Anthracene is one of the organic single crstals with unique optical and electronic properties reported first in 1948 [4]. In the present investigation, we made an attempt to grow pure crystal by adopting solvent evaporation technique using chloroform as a solvent. This paper deals about the mechanical and dielectric properties of anthracene crystal 2. Material Synthesis In our present study pure anthracene single crystals is grown by taking 50 ml of chloroform with measured quantity of anthracene powder (AR grade 99% pure) in a beaker and stirred continuously to yield saturated solution. The prepared solution was filtered using a sintered glass filter of 1µm porosity and the saturated solution is sealed with aluminium foil and the synthesized solution was kept in dark room without any mechanical disturbances. By repeated re-crystallization process good quality transparent single crystal is obtained within a period of 30 days. The photograph of the grown crystal is shown in Fig 1. Fig 1: As grown anthracene crystal 3. Results and discussion 3.1 Single crystal XRD Single crystal X-ray diffraction analysis for the grown crystal has been carried out to confirm the crystallinity and to identify the lattice parameters using ENRAF NONIUS CAD4 automatic X-ray diffractometer. The calculated lattice parameter values are a= 9.457 Å, b=6.04ͷ Å, c=ͺ.͸Ͷͳ Å, Ƚ, ɀ = ͻͲ˚ and Ⱦ=ͳͲ͵.͹˚ and the grown crystal is belong to monoclinic system with the space group P21/a [2]. The XRD results are in good agreement with reported value and thus confirms the grown crystal. 3.2 Micro hardness study Vickers microhardness number (VHN) was evaluated for anthracene crystal employing Futuretech FM- 800 type E-series microhardness tester for various loads ranging from 1-100 g. The value of Hv is calculated using the relation Hv= 1.8544 P/d 2 (1) where P is the applied load in g, d is the diagonal length in mm and Hv in kg/mm 2 . The variation of Hv with the applied load is shown in Fig 2. Fig 3 shows a plot of log P vs log d yields a straight line and the slope gives the work hardening coefficient Ǯnǯ. According to Onitsch [4], the work hardening coefficient Ǯnǯ should lie between ͳ and ͳ.͸ for harder materials and if the value of n is above 1.6 it comes