Structural and photoluminescence properties of Dy3+-doped KMgBO3 phosphors

A series (2, 4, 6 and 8 mol%) of Dy3+ ions-doped potassium magnesium borate phosphors were prepared by solid-state reaction method at 700 °C, with the aim of developing yellow wavelength emitting phosphors for white light-emitting diodes. The structural, morphological, optical and photoluminescence properties were analysed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), absorption spectrometer (UV–Vis) and spectrofluorimeter for all the prepared phosphors. From the XRD studies it was confirmed that, the undoped and Dy3+ ions-doped phosphor samples possess single-phase cubic crystal structure and P213 space group. From FTIR studies all the synthesized phosphor samples have metallic and BO3 bonds. In absorption studies, the absorption bands were identified in ultra-violet, visible and infrared region, and the energy band gap values were calculated for all the prepared samples. The excitation spectra of Dy3+ ions-doped phosphors were observed at 585 nm and it consists of four excitation bands. Among all the excitation bands 6H15/2 → 4F7/2 was the prominent excitation band, hence this transition has been used for obtaining emission spectra. In emission spectra three emission bands were identified at 485 (Blue), 585 (Yellow) and 661 nm (Red) corresponding to 4F9/2 → 6H15/2, 4F9/2 → 6H13/2 and 4F9/2 → 6H11/2 electronic transitions of Dy3+ ion. Among all these luminescence bands the strong intense emission band was observed at 585 nm. The luminescence intensity was enhanced with the increase of Dy3+ ion concentration up to 6 mol%, further enhancement of doping ion concentration decreased the luminescence intensity. In addition to CIE and CCT values were evaluated from emission spectra. The decay lifetime values were estimated for all the Dy3+ ions-doped phosphor samples. All these results recommended that the present prepared phosphor samples are well applicable for white colour light-emitting diodes and display applications.