Defect correlated fluorescent quenching and electron phonon coupling in the spectral transition of Eu_(3+) in CaTiO_3 for red emission in display application

摘要

This paper reports on the defect correlated self-quenching and spectroscopic investigation of calcium titanate (CaTiO_3) phosphors. A series of CaTiO_3 phosphors doped with trivalent europium (Eu~(3+)) and codoped with potassium (K~+) ions were prepared by the solid state reaction method. The X-ray diffraction results revealed that the obtained powder phosphors consisted out of a single-phase orthorhombic structure and it also indicated that the incorporation of the dopants/co-dopants did not affect the crystal structure. The scanning electron microscopy images revealed the irregular morphology of the prepared phosphors consisting out of μm sized diameter particles. The Eu~(3+) doped phosphors illuminated with ultraviolet light showed the characteristic red luminescence corresponding to the ~5D_0→~7F_J transitions of Eu~(3+). As a charge compensator, K~+ ions were incorporated into the CaTiO_3:Eu~(3+) phosphors, which enhanced the photoluminescence (PL) intensities depending on the doping concentration of K~+. The concentration quenching of Eu~(3+) in this host is discussed in the light of ion-ion interaction, electron phonon coupling, and defect to ion energy transfer. The spectral characteristics and the Eu-O ligand behaviour were determined using the Judd-Ofelt theory from the PL spectra instead of the absorption spectra. The CIE (International Commission on Illumination) parameters were calculated using spectral energy distribution functions and McCamy's empirical formula. Photometric characterization indicated the suitability of K~+ compensated the CaTiO_3:Eu~(3+) phosphor for pure red emission in light-emitting diode applications.