Growth and Characterization of ADP Single Crystal

Ammonium dihydrogen phosphate (ADP) (NH4H2PO4) single crystals were grown by gel method using sodium metasilicate (SMS). The X-ray diffraction analysis of the as–grown ADP crystals showed that it possess tetragonal structure having lattice parameters a = 7.502 °A and c = 7.554 °A. The Fourier transform infrared spectroscopy (FTIR) of as-grown ADP crystal taken between wave-number 400 to 4000 cm-1 showed peaks due to vibration and stretching of functional group O-N=P and –ONO2 in 485 to 902 cm-1, P=O and O-H in 1076 to 1544 cm-1 and O-H and N-H in 2400 to 3371 cm-1 range. The UV-Vis-NIR spectroscopy of ADP crystal showed direct optical bandgap of 4.99eV and indirect optical bandgap of 4.12eV. The optical microscopy employed to study the surface microstructure showed hillocks on the as-grown surfaces arising due to local increased supersaturation. The thermal properties of the as-grown ADP crystals were studied by thermogravimetric analysis (TGA). The thermal activation energy determined from the TGA curve using Broido, Piloyan-Novikova (PN) and Coats Redfern (CR) relations were in good agreement with each other. The obtained results are discussed in details.