Optically detected magnetic resonance study of an oxygen-vacancy complex in BaFBr

Abstract

BaFBr is usually contaminated with oxygen which influences the performance of this well known X-ray storage phosphor material. Oxygen is incorporated as a diamagnetic O2- ion on F- sites with a nearby charge-compensating vacancy in the Br- sublattice, as is known from the paramagnetic O-F and F(Br-) centres created by room-temperature X-irradiation and studied in detail with electron paramagnetic resonance (EPR) techniques. It is shown that BaEBr:O2-F has a luminescence band excited at 4.95 eV, peaking at 2.43 eV with two radiative lifetimes of 0.2 ms and 1 ms, respectively. With luminescence-detected EPR (i.e. optically detected magnetic resonance (ODMR)), it is shown that the luminescence is due to an excited triplet state of an O2-F-Br- vacancy pair. Time-resolved ODMR measurements reveal the same radiative lifetimes as seen in luminescence. No singlet emission was observed. The zero-field splitting can be explained assuming a F(Br-)-O-F pair defect as the excited triplet state.

Study on the hole-type traps in BaFCl:Eu2+ phosphor

“…O 2À acts as a hole trap and is stable at RT. Luminescence band due to O 2À is produced at 2.8 [1] or 2.43 eV [5], which are not overlapped with the 4f-5d Eu 2+ absorption band. Therefore, O 2À centers are not acting as recombination partners in the PSL process.…”

Photostimulation redshift for nonstoichiometric Ba1−xSrxFBr:Eu2+

“…The samples were tested for oxygen contamination by attempting to excite the luminescence due to O F 2Ϫ at 500 nm at low temperatures. 7 No O F 2Ϫ luminescence was observed. The grain size distribution was determined with a Coulter LS 130 apparatus.…”

Electron traps in Ca2+- or Sr2+-doped BaFBr:Eu2+ x-ray storage phosphors

“…The samples were tested for oxygen contamination by attempting to excite the luminescence due to O F 2Ϫ at 500 nm at low temperatures. 8 No O F 2Ϫ luminescence was observed. The grain size distribution was determined with a Coulter LS 130 apparatus.…”