Spectroscopic Analysis and Dosimetric Characterization of Lithium Fluoride (LiF) Crystals

Abstract

Lithium fluoride (LiF) is an inorganic, non-toxic, and chemically inert compound that has garnered extensive interest across scientific and industrial domains due to its exceptional physical, chemical, and optical properties. Crystallizing in a face-centred cubic (FCC) structure similar to sodium chloride (NaCl), LiF exhibits high thermal stability, with a melting point of 870 °C and a boiling point of 1676 °C. Its low refractive index (~1.4) and good infrared transmission make it ideal for optical applications, particularly in UV and IR spectroscopy. Furthermore, LiF demonstrates low solubility in water and moderate thermal conductivity (~12 W/m·K), reinforcing its stability in diverse environmental conditions.

A key application of LiF lies in radiation dosimetry, where it serves as a highly effective thermoluminescent (TL) material, particularly when doped with elements like magnesium, titanium, or copper (e.g., LiF:Mg,Ti and LiF:Mg,Cu,P). The presence of deep electron traps in its crystal lattice ensures prolonged retention of radiation-induced charge carriers, allowing for accurate and stable dose measurements over time. Importantly, the effective atomic number of LiF (Z_eff ≈ 8.2) closely matches that of human tissue, making it highly suitable for medical and environmental dosimetry.

The sol-gel method of the preparation of the phosphor, particularly the trifluoroacetic acid (TFA)-based route, offers a versatile pathway for preparing phase-pure, nanostructured LiF. This approach allows precise control over particle morphology and size through adjustments in solvent type, salt concentration, and organic surfactants, making it highly suitable for optimizing LiF's dosimetric and optical performance.