Mineralogical characterization and fluorescence properties of blue, yellow and green apatite

Abstract

Blue, yellow and green are common colors of apatite, and its mineralogical characteristics and fluorescence properties have attracted the attention of many researchers and scholars. In this paper, the structure, composition, spectroscopic features and fluorescence characteristics of three different colors of apatite are investigated to further compare and explore their mineralogical characteristics and fluorescence properties. The results show that the three colors of apatite that belong to fluorapatite, blue apatite and green apatite are in medium oxidation state, and yellow apatite is in oxidation state. Some samples of blue and green apatite showed the homogeneous substitution of [CO₃]²⁻ for [PO₄]³⁻. Yellow apatite fluoresces orange, green and blue apatite fluoresce blue–violet, and all three colors of apatite show strong emission peaks at 400 nm at an excitation wavelength of 320 nm, attributed to: the jump of Ce³⁺: (5d)⁵D_3/2 → ²F_7/2(4f) to (5d)⁵D_3/2 → ²F_5/2(4f), and the jump of Eu²⁺: 4f⁶5d¹ → (4f)⁸S_7/2; The emission peaks at 585 nm and 600 nm are attributed to the leaps of ⁴G_5/2 → ⁶H_7/2 for Sm³⁺ with ¹D₂ → ³H₄ for Pr³⁺. A comparative analysis of the relationship between luminescence intensity and temperature in samples of yellow and blue apatite was conducted. The findings of this analysis indicated that yellow apatite exhibits greater thermal stability in comparison to blue apatite.