Hee Dong Park

Effect of heat treatment on photoluminescence behavior of Zn2SiO4:Mn phosphors

Abstract The thermal treatment in reducing atmospheres gives rise to the increase both in emission intensity and 10% decay time in Zn 2 SiO 4 :Mn phosphors. The present investigation aims to take account of such changes in association with the structural change. For this sake, X-ray absorption spectroscopy techniques such as XANES and EXAFS were conducted to the Zn 2 SiO 4 :Mn phosphors. The Zn 2 SiO 4 :Mn phosphors were fired in the air and then thermally treated in two different reducing atmospheres (hydrogen or carbon). The photoluminescent (PL) behavior was closely related to the X-ray absorption data. The XANES and EXAFS prove that the oxidation state (+2) remains identical regardless of whether or not the samples are treated, but that the Mn–O distance was reduced by the heat treatment. In order to give a plausible interpretation to the change in PL results, two possible suggestions are presented. Firstly, it is conceivable that the thermally activated diffusion process of manganese ions splits Mn–Mn pair during the heat treatment. Another possibility is that the thermal treatment annealed out some quenching site, which is related with defects and impurities. Such hypotheses can be rationalized systematically by considering the results from lifetime measurement, Debye–Waller factor calculation, and XANES pre-edge peaks.

Effect of Co‐doping on the Photoluminescence Behavior of Zn2SiO4 : Mn Phosphors

The main objective of this investigation is to improve the photoluminescent performance of existing phosphors by adding a new co‐dopant. The candidate co‐dopants adopted in the present investigation are confined to substituents for the Zn site. In this context, the co‐doping effect of Mg and/or Cr upon emission intensity and decay time was studied in the present investigation. The co‐dopants incorporated into the phosphors are believed to alter the internal energy state so that the change in emission intensity and decay time could be expected. Both Mg and Cr have a favorable influence on photoluminescent properties, in particular, Mg enhances the intensity of manganese green emission and Cr shortens the decay time. The enhancement in emission intensity of , Mg phosphors was interpreted by taking into account the result from the DV‐Xα embedded cluster calculation. On the other hand, the energy transfer between Mn and Cr ions was found to be responsible for the shortening of decay time in phosphors.

Excitation energy-dependent photoluminescence behavior in Zn2SiO4:Mn phosphors

Abstract The photoluminescence (PL) property and energy transfer mechanism in Zn 2 SiO 4 :Mn phosphors were investigated in terms of excitation light wavelength. The concentration quenching experiment was performed, from which the critical distance of energy transfer was obtained. On the other hand, a calculation based on the spectral overlap was also carried out to obtain the critical distance by a different way. The critical distance from concentration quenching data was then compared to that from the spectral overlap data. The results from the concentration quenching data are not analogous to those from the spectral overlap data above a certain excitation photon energy, which implies that the conventional energy transfer scheme between Mn ions is no longer the rate controlling factor in the VUV range.