Synthesis, growth, optical, band gap energy and mechanical properties of semiorganic nonlinear optical material: 2-Aminopyridine potassium dihydrogen orthophosphate lithium chloride (2APKDPL) crystal

Abstract

2APKDPL salt was synthesized by taking equimolar ratio (1:1:1) of 2-aminopyridine, potassium dihydrogen orthophosphate and lithium chloride by slow evaporation technique. Optimum level of purity is achieved by successive recrystallization process. Solubility curve was drawn gravimetrically for different temperature with time interval 5 °C from 30 °C to 55 °C. Optically good quality 2APKDPL crystal of moderate size 9 mm × 4 mm × 2 mm was harvested over the period of 75 days. The functional groups presences in the crystallized 2APKDPL sample were identified by Fourier Transform Infrared (FTIR) spectroscopy. A well defined sharp Bragg’s peak in powder X-ray diffraction analysis identifies the crystalline nature of the grown sample. Single crystal X-ray diffraction study reveals that the 2APKDPL crystal belongs to tetragonal crystal system with noncentrosymmetric space group I4. UV–vis-NIR spectrophotometer study shows the cut-off wavelength of the grown samples as 262 nm and the optical band gap (Eg = 4.62 eV) was calculated for 2APKDPL crystal. SHG efficiency of 2APKDPL is 1.14 times than that of standard potassium dihydrogen phosphate (KDP). The work hardening coefficient (n = 0.5) of 2APKDPL crystal confirming that the grown 2APKDPL crystal belongs to hard category. The mechanical properties, Stiffness constant (C11), Yield Strength (σy), Fracture toughness (Kc), Brittleness index (Bi), Tensile Strength (T) and Yield Point (Y) are calculated and the corresponding graphs were plotted. The dielectric constant and dielectric loss of grown 2APKDPL crystal have been studied. EDAX study was carried out to identify the presence of metal ion in 2APKDPL crystal. The growth mechanism of 2APKDPL crystal was analysed by chemical etching process. Keywords: Solution growth, Optical band gap, Mechanical properties, EDAX