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[18p-G204-6] Control of bandgap energy and photoluminescence properties of Pr3+-acitvated perovskite phosphors
Keywords:phosphor, photoluminescence, oxynitride
In this study, we investigated the photoluminescence of Pr3+-acitvated CaZrxTa1-xO2+xN1-x phosphors1) with the range from 0.0 to 1.0. This solid-solution system can be expected that the wavelength of maximum exciation are widely adjusted along with bandgap energy between valence and conduction bands by the control of the O/N and Zr/Ta ratios. Thus, the sharp emission peak from Pr3+ in the solid-solution system can be excited by near-UV or blue lights if the width of bandgap energy is adujusted from 2.8 to 3.2 eV. All the sample were prepred by polymerizable complex method. The obtained precursors were heat-treated under NH3 gas flow at 900-1100oC. XRD patterns indicated that all the samples were of single phase perovskite structure. XRD patterns also show the shift of diffraction peaks to low angle region by increasing with Zr4+ concentaration. The absorption attributed to the band gap excitation shifted to high-energy sides with increasing Zr4+ concentration. Especially, the bandgap energy were sucessfully adjusted from 2.8 to 3.2 eV while the x was changed from 0.70 to 0.90 by the control of the Zr4+/Ta5+ and O/N ratios. Furthremore, the solid-solution system showed the intriguing photoluminous behavior. The single emission peaks were observed at 612 nm when the bandgap enegries were adjusted at around 3.0 eV for the samples with x from 0.55 to 0.70, The red emission peak can be assigned to the electron transition between 1D2 and 3H4 levels of Pr3+ ions. In contrast, when the bandgap energy became larger than 3.0 eV, the PL spectra was gradually changed. Several emission peaks were observed in the range from 490 to 750 nm, which can be assinged as the electron transition between 3P0 to 3H4, 3H5 and 3F2 levels.2) This behavior can be atributed to the width of the bandgap energy of the host compounds.