Photoluminescence properties of thenardite activated with Eu

Abstract Na 2 SO 4 :Eu phosphors were prepared by heating pure natural thenardite with EuF 3 at 900 °C for 20 min in air. The photoluminescence (PL) and excitation spectra of as-prepared and γ-ray-irradiated phosphors were observed at 300 K. The PL spectrum under 394 nm excitation consisted of strong narrow bands with peaks at 579, 592, 616, 652, 697 and 741 nm, assigned to the 5 D 0 → 7 F J ( J =0, 1, 2, …, 5) transitions, respectively, within Eu 3+ . The PL spectrum under 340 nm excitation consisted of a broad Eu 2+ band with a peak at 435 nm. The excitation spectrum obtained by monitoring the violet luminescence consisted of a weak band with a peak at approximately 261 nm and a broad Eu 2+ band with a peak at approximately 338 nm. The relative efficiency of the violet luminescence of the γ-ray-irradiated phosphor at the exposure of 46 kGy increased up to 3.0 times that of the unirradiated phosphor. The enhancement of violet luminescence by γ-ray irradiation was ascribed to the conversion of Eu 3+ to Eu 2+ in Na 2 SO 4 .