Eu3+ luminescence—a structural probe in BiCa4(PO4)3O, an apatite related phosphate

Dependence of Eu3+ luminescence dynamics on the structure of the combustion synthesized Sr5(PO4)3F host

“…The 5 D 0 → 7 F 0 line has been observed in the compounds with a strongly covalent Eu-O bond and this favors a higher intensity [14]. One can note that the intensity of the 5 D 0 → 7 F 0 transition is weak in our case and it appears as a shoulder band at the same position as reported previously for an Eu-apatite structure [10][11][12][13][14]. The possibility of occurrence of pure red emission and suppression of the 5 D 0 → 7 F 0 transition in the sample can be based on charge compensation and site symmetry distribution.…”

“…The PL emission spectrum ( exc = 243 nm) consists of the major peak at 616 nm that can be ascribed to the 5 D 0 → 7 F 2 transition of Eu 3+ and other peaks at 590, 653, 680 and 705 nm to the 5 D 0 → 7 F 1 , 5 D 0 → 7 F 3 and 5 D 0 → 7 F 4 transitions of Eu 3+ , respectively. The abnormal feature of the Eu-apatite structure appears as a shoulder and is observed at 578.7 nm corresponding to the 5 D 0 → 7 F 0 transition [10][11][12][13][14]. The 5 D 0 → 7 F 0 transition is normally forbidden and will be present only when Eu 3+ ion occupies sites with local symmetries of C 3 or C s [12].…”

“…The 5 D 0 → 7 F 0 transition is normally forbidden and will be present only when Eu 3+ ion occupies sites with local symmetries of C 3 or C s [12]. The 5 D 0 → 7 F 0 line has been observed in the compounds with a strongly covalent Eu-O bond and this favors a higher intensity [14]. One can note that the intensity of the 5 D 0 → 7 F 0 transition is weak in our case and it appears as a shoulder band at the same position as reported previously for an Eu-apatite structure [10][11][12][13][14].…”

“…The origin of two contributions can be confirmed from the time resolved spectroscopy. According to several literature studies [12,14,24,25], Eu 3+ substitutes Sr 2+ ions and occupy mainly the S2 sites, with a relative abundance of 60% which makes 5 D 0 → 7 F 0 transition more intense compared to other transition of Eu 3+ . In our case observed 5 D 0 → 7 F 0 emission band at 578.7 nm is related to S1 sites, with a relative abundance of 40%.…”

“…This situation is further favored when the charge compensation occurs by an oxygen ion on the fluorine site. The intense 5 D 0 -7 F 0 transition gives rise to yellow-red emission [13,14]. Although, this transition allows significant insights in the local structural site symmetries, yet, it has a limited spectroscopic advantage in terms of a prominent 0925-8388/$ -see front matter © 2010 Elsevier B.V. All rights reserved.…”