Luminescence properties of ZnB2O4:Pb2+ phosphors: Suppression of concentration quenching
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The UV-A emitting ZnB2O4:Pb2+ crystalline powder phosphors were produced using the conventional solid-state reaction synthesis technique at 830 °C for 6 h in air. The morphology and structure of the phosphors were explored by SEM, XRD and FT-IR analyses. The optical properties of the phosphors were examined by UV–vis diffuse reflectance and steady-state photoluminescence (PL) analyses. The excitation and emission bands of Pb2+ doped ZnB2O4 was observed at 304 nm and 388 nm, respectively. The effects of dopant concentration on the PL emission intensities of Zn1–xPbxB2O4 (0 ≤ x ≤ 0.15) phosphors were studied. The well-known concentration quenching phenomenon was not observed in the studied range. To explain the observation of suppressed concentration quenching the energy transfer between radiative and non-radiative centers has been discussed. Based on the absorption, excitation and emission results of the samples, a tentative configurational coordinate-energy diagram was proposed. Obtained results show that the ZnB2O4:Pb2+ phosphor is a good candidate for UV-A applications as a rare-earth free wavelength converter.