Structural characterization studies on the natural mineral pyrophyllite

A light-yellow-colored pyrophyllite (Al₂O₃·SiO₂) mineral obtained from Vempalli, Cuddapah district, Andhra Pradesh, India, is investigated in the present work. Chemical analysis carried out using energy-dispersive spectroscopy (EDX) shows that Fe₂O₃ is present by about 1.56?wt%. Structural characterization was performed using X-ray diffraction (XRD). XRD results suggest that the unit cell is monoclinic with a = 5.16, b = 8.798, c = 9.347 Å and β = 100.46°. The ligands around the metal ion present in the structure are investigated using FTIR spectroscopy. EDX analysis indicates that iron and titanium are only two transition metals present in it. Morphology studied using scanning electron microscopy suggests that the unit cell consists of a dioctahedral layered structure. Fe³⁺ is present in the location of Al³⁺ in the unit cell of pyrophyllite. Electron paramagnetic resonance results indicate that the unit cell of the crystal contains Fe(III), and its g values are found to be 4.10 and 2.0. Infrared properties are due to the presence of silicate and hydroxyl anions as ligands. Nonlinear optical measurements carried out using Z-scan reveal the occurrence of strong nonlinear optical limiting in the material, indicating potential applications in laser safety devices.