Synthesis of novel Eu2+ activated K3Ca2(SO4)3F down-conversion phosphor for near UV excited white light emitting diode

Abstract

In the present paper, we have successfully synthesized Eu2+ activated K3Ca2(SO4)3F phosphor by two-step solid-state reaction method at high temperature (800 °C). Pure crystalline formation, morphological behavior, and their vibration bonds of synthesized Eu2+ activated K3Ca2(SO4)3F phosphor were verified by the X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Fourier transform Infrared Spectrum (FT-IR). The photoluminescence (PL) spectrum and CIE coordinate with color purity also characterized. In PL emission spectra clearly represented that broad excitation band from 250 nm to 400 nm ranged. The center of this PL excitation spectra observe at 326 nm, but some parts of these spectra lies to 350 nm–400 nm. This excitation wavelength is very useful for the generation of white light because it may be used as near UV light. PL emission represents broad emission spectra from 400 nm to 550 nm centred at 440 nm. Most part of these PL emission spectra lies in the blue region of the spectrum. PL spectra arise from the transitions between the 5d and 4f orbital’s transition of Eu2+ ions. EVI parameters such as Stokes Shift (ΔEs), the Huang-Rhys factor (S),effective phonon energy (ħω) and the Zero-phonon line (ZPL) are calculated. In our present work, we are calculated that the value of Huang–Rhys factor constant (S) is 3.74 that means coupling is intermediately strong. CIE chromaticity coordinate of K3Ca2(SO4)3F:xmol%Eu2+[x = 0.5, 2.0, 3.0, 5.0, 7.0, 10mol%] phosphor were also calculated by using OSRAM SYLVANIA color calculator 1931. By using these CIE chromaticity coordinate was calculated the value of color purity for each concentration of Eu2+ ions. After seeing all results of synthesized phosphor material we are concluded that it may be a better option used as commercial phosphor for obtaining white light. So it may be a promising candidate for NUV WLEDs.