Laser-Induced breakdown spectroscopy and Energy-Dispersive X-ray analyses for green mineral fluorite (CaF2)
Amir Fayyaz, Haroon Asghar, Tahani A. Alrebdi
Abstract
Laser-induced breakdown spectroscopy (LIBS) technique was utilized to study the green mineral fluorite (CaF2) samples. The LIBS experiment was performed using Nd: YAG Laser system and a linear array CCD detector coupled with an Avantes spectrometer in an air atmosphere. The optical emission spectra of ten different fluorite samples were studied. The molecular bands correspond to the green B2Σ+-X2Σ+ and orange A2Π-X2Σ systems of the diatomic CaF-molecule, specifically at Δν = -1, 0, +1 sequences and the CaO diatomic molecule between 618 nm and 630 nm were detected. It was observed that the CaF-diatomic molecular emission bands exhibited stronger optical emission compared to the fluorine (F) atomic lines. Chemical composition (wt.%) analysis was acquired using CF-LIBS methodology under optically thin and local thermodynamic equilibrium (LTE) conditions. Our CF-LIBS studies revealed that Ca (50-60%) and F (30-40%) were the major elements, while C (3-5%) and O (2-5%) were minor elements present in all samples. For comparison, we employed energy-dispersive X-ray (EDX) spectroscopy to study the elemental composition (wt.%). The results obtained from CF-LIBS were in good agreement with those obtained from the EDX technique. To validate CF-LIBS results, the calibration curve method was employed using the validated samples (S3, S5, and S7). Furthermore, we utilized principal component analysis (PCA) on the LIBS spectral data to classify the fluorite samples.