| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1881576 | Radiation Measurements | 2010 | 4 Pages |
The series of whitlockite compounds Ca3(PO4)2 and Ca9Ln(PO4)7 (Ln = Pr, Eu, Tb, Dy, Ho, Er, Lu) was studied in radioluminescence (RL) and thermally stimulated luminescence (TSL) excited by X-rays. f-f emission lines of Ln3+ were observed in RL for Ca9Ln(PO4)7 (Ln = Pr, Eu, Tb, Dy, Ho, Er) whereas d-d emission band of the impurity Mn2+ was observed in Mn:Ca3(PO4)2 and Mn:Ca9Lu(PO4)7 at 655 nm. In TSL, the Eu, Ho and Er compounds did not show any signal. As Eu3+, Ho3+ and Er3+ present the highest Ln3+/Ln4+ ionization potential (IP) of the series, this was interpreted as the inability of these lanthanides to trap a hole. On the contrary Pr3+ in Ca9Pr(PO4)7, Tb3+ in Ca9Tb(PO4)7, Dy3+ in Ca9Dy(PO4)7, Mn2+ in Mn:Ca3(PO4)2 and Mn:Ca9Lu(PO4)7 were identified as hole traps and radiative recombination centers in the TSL mechanism. Ca9Tb(PO4)7 was found to be a high intensity green persistent phosphor whereas Mn:Ca9Lu(PO4)7 is a red persistent phosphor suitable for in vivo imaging application.
