The role of silver in the radiophotoluminescent properties in silver-activated phosphate glass and sodium chloride crystal

We have systematically investigated the X-ray-induced radiophotoluminescence (RPL) bands in a silver-activated phosphate glass (PG:Ag), and we have ascribed these bands to Ag0, Ag2+ and Ag2+ centres, using optical characterisation such as absorption, excitation, emission and lifetime measurements. The absorption spectrum of PG:Ag irradiated with X-rays was decomposed into six Gaussian bands on the basis of its strong analogy with irradiated silver-activated sodium chloride (NaCl:Ag). We confirmed that blue emission peaking at 450 nm was connected with the 270 and 345 nm bands of the excitation spectrum, while orange emission peaking at 560 nm was associated with the 308 nm excitation band. Each band of the excitation spectrum was in turn attributed to an Ag2+, Ag0 or Ag2+ centre by analogy with the RPL of NaCl:Ag. The excited-state lifetimes for each emissive process were also determined for different X-ray doses. In conclusion, we determined that both blue and orange emissions result from radiation-induced (rather than intrinsic) properties in the range of 1.22–24.5 Gy.