Title: Growth and morphological studies of squaric acid doped lithium sulfate monohydrate single crystal for nonlinear optical and piezoelectric applications
Pure and squaric acid doped lithium sulfate monohydrate single crystals have been successfully grown by slow evaporation method. External morphology of the pure and squaric acid doped crystal was explained using geometrical consideration with modified Bravais-Friedel-Donnay-Harker (BFDH) law. The growth rates of squaric acid doped crystal planes were effected as compared with pure material. UV-Vis spectra showed the increase in transmittance of squaric acid doped crystal. Photoluminescence study was conducted to observe the change in emission as result of squaric acid doping. FTIR analysis confirmed the presence of squaric acid dopent molecules in grown crystal. Dielectric study with temperature was performed to understand its variation of any structural phase with squaric acid dopant molecules in titled crystal. The piezoelectric coefficient d33 values of pure and squaric acid doped crystal were found to be 5 pC/N and 7 pC/N along . Mechanical strength was analysed by Vicker’s microhardness. Weibull statistical distribution was used to statistically analyze the variability of hardness number. Mechanical strength of the SA doped LSMH crystal was increased. The values of Meyer’s index ‘n’ in hardness analysis are found to be 2.04 and 1.92 for pure and doped crystal, respectively, which suggested that the crystal become hard as a result of doping. Weibull plot showed that at low indentation loads there is large Hv data points scattering and the variability of Hv data reduced at large indenter loads. For both pure and doped LSMH crystals, no structural phase transformations were induced after indentation.
Dr. Harsh Yadav is an Assistant Professor in the Department of Physics, Netaji Subhas University of Technology, New Delhi, India. He earned his M.Sc. (Physics) from IIT Delhi and a Ph.D. specializing in single crystal growth using Czochralski technique and device fabrication at the Department of Physics & Astrophysics, University of Delhi. His research focuses on the development of new multifunctional materials and understanding the structure-property relationships for piezoelectric, ferroelectric, nonlinear optical, electrical properties of single crystals and their relation with intermolecular interactions and crystals defects. He developed a new concept to determine the crystal morphology using the propagation vector of centre of mass of the molecular basis in lattice. Dr. Yadav has fabricated a low cost modified Czochralski set-up for the bulk single growth of organic materials. He designed various types of patch antenna based on single crystal substrate for wireless communication and energy harvesting applications. He has published 35 research papers in international journals, 1 book and 3 conference proceedings.