Red long-lasting phosphorescence (LLP) in β-TCP type Ca9.5Mn(PO4)7 compounds

Mn-ion doped calcium phosphates namely Ca5(PO4)3(OH) hydroxyapatite (HAP), β-Ca3(PO4)2 (β-TCP) as well as Ca9.5Mn(PO4)7 whitlockite were synthesized and the optical properties of the Mn2+ cations were investigated. Annealing under reducing atmosphere enhances the emission of the divalent manganese species. Electron paramagnetic resonance (EPR) and optical spectroscopies confirm that Mn2+ ions are the active species. Orange and red emissions occur respectively for the Mn:HAP and Mn:TCP. For this latter, long-lasting phosphorescence (LLP) coming from the Mn2+ emission (4T1 → 6A1 transition) is observed at 640 nm but it appears that the traps depths are either two shallow or too deep to lead to an efficient long-lasting emission.

► Red long-lasting phosphorescence (LLP).
► β TCP type Ca9.5Mn(PO4)7 compounds.
► Thermoluminescence study of materials.
► Mn2+ EPR and optical spectroscopies.
► Materials for optical imaging.