Coromandal Journal of Science, Vol. 2, No. 1, June 2013. pp.20-24. Optical, Thermal and Mechanical Properties of Mono Ammonium Phosphate (MAP) Single Crystal B. Neelagantaprasad 1 , A. Jegatheesan 2 , C. Sadeeshkumar 3 , T. Jayanalina 4 and B. Ravi 5 1,4 Department of Physics, K.S.R. College of Engineering, Tiruchengode, Tamilnadu, India. 2 Deptartment of Physics, Paavaai Group of Institutions, Pachal, Namakkal, Tamilnadu, India. 3 Department of Physics, Gnanamani College of Technology, Namakkal, Tamilnadu, India. 5 Department of Physics, Vivekanandha Institute of Engineering and Technology for women, Tiruchengode, Tamilnadu, India. Email: 1 bnprasadns@gamil.com ABSTRACT Mono Ammonium Phosphate (NH 4 H 2 PO 4 ) or Ammonium Dihydrogen Phosphate(ADP) single crystals were grown by slow evaporation technique at 30° C. The X-ray diffraction analysis of the as–grown MAP crystals showed that it possess tetragonal structure having lattice parameters a =b= 7.502 °A and c = 7.554 °A. The Fourier transform infrared (FTIR) spectroscopy of as-grown MAP crystal was taken between wave-number 400 and 4000 cm -1 showed peaks due to vibration and stretching of functional group O-N=P and –ONO 2 in 545 to 906 cm -1 , P=O and O-H in 1100to 1642 cm -1 and O-H and N-H in 2874to 3249 cm -1 range. The lower cut off wavelength of MAP crystal occurs at 198 nm and it reveals that the material has good optical transparency in the entire visible region. Thermal studies (TGA/DTA) confirm that there is no weight loss up to ~682C. The hardness of the grown crysal was determined by using Hv=1.8544 p/d 2 . The morphology of the grown crystal was studied by scanning electron microscope (SEM). Keywords— Slow evaporation technique, Optical, Thermal and Mechanical properties. 1. INTRODUCTION Monoammonium phosphate (NH 4 )H 2 PO 4 is an interesting material and it belongs to isomorphous series of phosphates and arsenates that presents a strong piezoelectric activity [1-4]. MAP is antiferroelectric below 148.5 K and belongs to P21 21 21 space symmetry group, while above this temperature it becomes paraelectric having I 4/2 d symmetry [5-7]. Monoammonium phosphate (NH 4 H 2 PO 4 ), is formed when a solution of phosphoric acid is added to ammonia until the solution is distinctly acidic. It crystallizes in quadratic prisms. Monoammonium phosphate is often used in the blending of dry agricultural fertilizers. It supplies soil with the elements nitrogen and phosphorus in a form which is usable by plants. Currently,KH 2 PO 4 (KDP) and NH 4 H 2 PO 4 (MAP) are the available nonlinear crystals needed for laser radiation conversion in laser fusion system. Laser fusion research needs large plates of nonlinear crystals for electro-optic switches and frequency converters. The properties of potassium dihydrogen orthophosphate (KDP) and its analogs include transparency in a wide region of the optical spectrum, resistance to damage by laser radiation and relatively high nonlinear efficiency, in combination with reproducible growth to large size and easy finishing [8].Studies on ammonium dihydrogen phosphate (MAP) crystals still attract interest because of their unique non-linear optical, dielectric and antiferroelectric properties and their varied uses as electro-optic modulator, harmonic generators and parametric generator. They are still widely used as nonlinear optical devices and the choicest electro – optic materials having wide practical application [9-20]. Several researchers have carried out a lot of studies on pure MAP crystals [21-23]. Studies have also been made about the effect of mixing of divalent and trivalent impurities on the growth, habit modification and structure of MAP [24-27].In this research article, we have presented some aspects on the optical, thermal and mechanical properties of MAP single crystal. 2. EXPERIMENTAL DETAILS 2.1 Crystal Growth Crystal growth of pure MAP was done by slow evaporation solution growth technique at room temperature. Analytical grade MAP has been re- crystallized thrice to extract pure MAP. Saturated MAP solution was prepared using water as solvent. Equal amount of MAP solution was poured into beakers. MAP solution were thoroughly mixed, stirred, filtered and