BaWO4: Pr single crystals co-doped with Na

Abstract Single crystals of undoped BaWO4, BaWO4: 0.5 at.% Pr, 1 at. % Na and BaWO4: 1 at.% Pr, 2 at.% Na were grown from an inductively heated iridium crucible by the Czochralski method on a Malvern MSR4 puller. They were investigated using X-ray diffraction (XRD), electron paramagnetic resonance (EPR) and optical spectroscopy methods. EPR measurements have shown several point defects of C2 axial symmetry, assigned to F-type color centers. The crystal reveals an anomalous magnetic behavior at about 109 K, and magnetic susceptibility increasing with temperature. The dominating magnetic interaction is antiferromagnetic-like. Strong red photoluminescence (PL) has been found centered at 647 nm while excited with 450 nm due to the 3P0-3F2 transition. Only intra-configurational 4f2-4f2 transitions were observed. Photoluminescence excitation (PLE) spectra were composed of four bands peaking at 450, 475, 489 and 495 nm, corresponding to 3P2, 3P2 + 1I6, 3P1, 3P0 levels respectively. Photoluminescence decay times for 3P0 → 3H4 and 1D2 → 3H4 radiative transitions, radioluminescence (RL), thermoluminescence (TL) and light yield (LY) investigations were analyzed. Four first-order discrete TL peaks for BaWO4: Pr, Na. with maxima at about 65, 75, 140 and 235 K have been found. Trap parameters were calculated. Unfortunately, no photopeaks were resolvable.