Growth of high-quality organic single crystal of 2-aminopyridinium 4-nitrophenolate 4-nitrophenol (2AP4N) by a novel Rotational Sankaranarayanan–Ramasamy (RSR) method

Abstract

The good quality 2-aminopyridinium 4-nitrophenolate 4-nitrophenol (2AP4N) single crystals have been grown by (i) Sankaranarayanan–Ramasamy (SR) method and (ii) Rotational Sankaranarayanan–Ramasamy (RSR) method. The effect of rotation on unidirectional crystal growth method (RSR) has been reported for the first time. The apparatus was specially designed and developed for the growth of high-quality crystals by slow cooling under rotational conditions. The high-quality crystals have been achieved under forced convection and the quality of the crystal is compared to the crystals grown under free convection conditions. The crystal structure was analyzed by single crystal X-ray diffraction (SXRD) measurement. The grown crystal was subjected to the powder X-ray diffraction (PXRD) analysis to confirm the growth direction along (0 0 1) plane. The optical quality of the grown crystals has been analyzed by UV–Vis NIR spectrophotometer. It confirms that the grown crystal is highly transparent in the visible and near IR region. The photoluminescence behaviour was recorded in the wavelength region between 450 and 700 nm. It confirms that the grown crystal has emission at 500 nm. The electro-optical properties of the grown crystal were analyzed by photoconductivity measurement and it has positive photoconductivity nature. The grown crystal has less dislocation densities as confirmed by chemical etching analysis. The mechanical strength was investigated by Vickers microhardness tester. The frequency dependent dielectric properties of the crystals were investigated. The laser damage threshold (LDT) was measured for both SR and RSR method grown crystals. The full-width at half maximum (FWHM) of high-resolution X-ray diffraction (HRXRD) curves indicate that the grown crystal has high crystalline perfection. The results obtained from the SR and RSR method grown 2AP4N crystals were compared. The RSR method grown crystal has higher optical transparency, higher photoluminescence, higher photoconductivity, higher mechanical strength, higher laser damage threshold, higher crystalline perfection, less dislocation density, low dielectric loss and low full with at half maximum (FWHM). The second harmonic generation (SHG) of 2AP4N was analyzed by Kurtz-Perry powder technique. The SHG efficiency was found to be 4.5 times that of reference KDP material. The above studies reveal that the RSR method grown crystals are more useful for device applications.