Oxidation states, optical and electronic properties of Eu and Tb doped nano-fluorapatite phosphor by self-propagating combustible approach

In this work, oxidation states, optical and electronic properties of Eu and Tb ions in Ca 5 (PO 4 ) 3 F nano–fluorapatite by self–propagating combustible approach has been reported. Fluorapatite is the most common phosphate mineral. It commonly occurs as a detrital or digenic mineral. Herein, nano–fluorapatite is synthesized by using self–propagating combustible approach. The synthesized nano–fluorapatite is characterized by XRD, SEM, Absorption, PL, CL, AES, and XPS analysis. The crystal structure of Ca 5 (PO 4 ) 3 F fluorapatite is reported as hexagonal phase with space group of P6 3 /m. Structural parameters are reported by using Rietveld refinement analysis to validate the crystalline analysis of the fluorapatite. A minor change in the unit cell parameters of synthesized fluorapatite is reported. The photoluminescence (PL) spectrum exhibits Eu 2+ along with Eu 3+ emission at CT band of UV excitation. The prominent sharp emission peak at 615 nm associated to orange-red emission of Eu 3+ ion and broad band at 350–550 nm suggests blue–green emission associated with Eu 2+ ion. Similarly, Tb 3+ ion shows characteristics narrow emission peaks at 489, 543 and 620 nm at CT band of UV excitation. The CL spectrum also recorded to confirm the identical emission behaviour with prominent CL intensity. Eu ion present as Eu 2+ and Eu 3+ oxidation states, while Tb as Tb 3+ and Tb 4+ states responsible for PL and CL emission revealed from the XPS analysis along with the bonding in the host matrix. The life time decay analysis of Eu 2+ , Eu 3+ and Tb 3+ ion confirms the prominent luminescence behaviour and CIE coordinates reported the true colour of the nano–fluorapatite phosphors. Judd-Ofelt intensity parameters of Eu and Tb doped Ca 5 (PO 4 ) 3 F phosphor indicates that the calculated theoretical parameters are well matched with the experimental data.