Luminescence spectra of doped and undoped lead tungstate crystals

TL spectra of undoped lead tungstate crystals exhibit glow peaks at 30 K and 85 K centred at 440 nm, plus a peak at 50 K at 530 nm in an annealed sample. Annealing adds a 170 K peak. Trivalent dopants of La3+ and Y3+ reduce the green luminescence, and Nb5+ introduces a peak near 100 K centred at 530 nm; Sb introduces features between 40 K and 90 K and 150 and 180 K. The luminescence emissions around 50 K may be attributed to complex intrinsic defect centres, including (WO4)(-3) . Of the four dopants studied in the present research, Sb+5 has the highest luminescence intensity. CL spectra show interesting anomalies near 170 K which are linked to a phase change of water/ice nanoparticles trapped at dislocations.