Growth and characterization of tetramethyl ammonium tetrachloro zincate II: A ferroic crystal S. Devashankar, L. Mariappan, P. Sureshkumar, M. Rathnakumari à Materials Research Centre, Department of Physics, Velammal Engineering College, Tamilnadu, Chennai 600 066, India article info Article history: Received 1 May 2009 Received in revised form 6 June 2009 Accepted 10 June 2009 Communicated by M. Schieber Available online 7 July 2009 PACS: 61.05.cp 68.35.Gy 68.35.Rh Keywords: A1. Crystal morphology A1. X-ray diffraction A2. Growth from solution B1. Zinc compounds B2. Ferroelectric materials B2. Nonlinear optical materials abstract Ferroic crystals of tetramethyl ammonium tetrachlorozincate (TMA-ZnCl) were grown by slow evaporation technique and the morphology of the grown crystals varies with different pH values. The compound crystallizes in orthorhombic primitive system at room temperature with non-centro symmetric space group Pmna. The grown crystals were subjected to powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible–near-infrared (UV–vis–NIR) spectral studies and thermal studies. Differential scanning calorimetry (DSC) measurement confirms the existence of structural phase transition and the thermogravimetric analysis (TGA) studies reveals that the crystal is thermally stable up to 330 1C. Vicker’s microhardness studies expose that the material is mechanically stable up to a load of 60 g. The laser second harmonic generation (SHG) efficiency of the grown crystal was found to be 1.3 times that of potassium dihydrogen orthophosphate (KDP) crystal. & 2009 Elsevier B.V. All rights reserved. 1. Introduction Ferroic is the generic name given to the study of ferromagnetic materials, ferroelectric materials, ferroelastic materials, ferrogyro- tropic materials, ferromagnetoelastic materials, ferromagnetoelectric materials, ferrobielastic materials, etc., [1]. The term Ferroic was coined in the year 1969 by Aizu [2]. Potassium dihydrogen orthophosphate (KDP), ammonium dihydrogen orthophosphate (ADP), triglycine sulphate are few representative ferroelectric materials that were studied for a long time for their interesting nonlinear optical (NLO) properties. A 2 BX 4 type ferro electric materials like potassium selenate (K 2 SeO 4 ), potassium zinc chloride (K 2 ZnCl 4 ) and rubidium zinc chloride (RbZnCl 4 ) were widely studied materials for their interesting incommensurate–commensurate transitions [3–5]. Crystals with tetramethyl ammonium groups with the common chemical formula [N(CH 3 ) 4 ] 2 MX 4 , where M is a divalent metal cation such as Zn 2+ , Mn 2+ , Cu 2+ , Cd 2+ , Ni 2+ and Hg 2+ and X a halogen Cl 1 or Br 1 , which belongs to A 2 BX 4 type have been widely studied for their ferroic nature (ferroelectric and ferroelastic) [6–8]. Of these, many of the chloride compounds exhibit a number of successive structural phase transitions at low temperatures, which are associated with the reorientation dynamics of the tetra methyl ammonium groups with some small distortion of the inorganic chains. These phase transitions include ferroelectric–ferroelastic, commensurate–incommensurate and order–disorder transitions [9–11]. These crystals had attracted the attention of device oriented Physicist for its switchable elastic, electric and optical properties [12]. Among these crystals, tetramethyl ammonium tetrachloro zincate (abbreviated as TMA-ZnCl) shows much scientific interest as model systems with incommensurate modulation [13]. Tetramethyl ammonium tetrachloro zincate crystals found to exhibit many nonlinear phenomena such as temperature depen- dence of birefringence, thermooptic memory, piezooptic and electrooptic effect. Iizumi and Gesi [14] have determined the crystal structure of tetramethyl ammonium tetrachlorozincate (TMA-ZnCl) through X-ray diffraction (XRD) at room temperature and it belongs to orthorhombic system with space group Pmna. Structural phase transitions in this crystal were studied by many researchers using different methods [15–18]. Several researchers had earlier investigated the ferroelastic domain structure of the crystal [19–21]. Birefringence studies were also carried out by many researchers [20,22,23]. From the literature survey, it shows ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jcrysgro Journal of Crystal Growth 0022-0248/$ - see front matter & 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jcrysgro.2009.06.056 à Corresponding author. Tel.: +9144 26591860; fax: +9144 26591771. E-mail addresses: mrathnakumari@yahoo.com, hod.phy@velammal.org (M. Rathnakumari). Journal of Crystal Growth 311 (2009) 4207–4212