XRD, TEM, EPR, IR and Nonlinear Optical Studies of Yellow Ochre

Yellow ochre mineral obtained from Vempalli mandal, Cuddapah district, Andhra Pradesh of India is investigated in the present work. Its chemical analysis indicate that Fe2O3=4.22 wt% and TiO2=0.64 wt%. Structural characterization is performed using X-ray diffraction (XRD). XRD results suggest that goethite (Fe2O3) and quartz are present. Among them goethite is the major constituent. Its unit cell is orthorhombic with a=4.14, b=10.0, c=3.03A. The ligands around the metal ion present in the structure are investigated using FTIR spectroscopy. Internal structure studied using TEM suggests that the mineral consists of needle shaped iron oxide nano particles and quartz formed as tetrahedral and octahedral layers. EPR results indicate that the unit cell of the crystal contains Fe(III), and its g values are found to be 4.19 and 2.13. FTIR properties are due to the presence of silicate and hydroxyl anions as ligands. Nonlinear optical measurements carried out using Z-scan reveal the presence of strong nonlinear optical limiting in the material, indicating potential applications in laser safety devices.