Enhanced red down-conversion luminescence and high color purity from flux assisted Eu3+ doped calcium aluminozincate phosphor

Abstract

Trivalent europium ions (Eu3+) doped calcium aluminozincate (CAZ) phosphors blended with various fluxes (NaF, NaCl and Na2B4O7) have been synthesized by conventional solid-state reaction method. The structural, morphological and luminescent properties along with lifetimes have been investigated in detailed. The Judd-Ofelt (J-O) analysis has been carried out to get insight of optical properties. The X-ray diffraction (XRD) pattern confirms the single phase orthorhombic structure for Eu3+ doped CAZ phosphor with NaCl and Na2B4O7 fluxes; whereas the phase purity has not been achieved in NaF assisted Eu3+ doped CAZ phosphor. The as-synthesized phosphor has uneven agglomerated micron sized particles. The photoluminescence (PL) studies exhibit significant enhancement in the red emission for Eu3+ doped CAZ phosphor with the addition of Na2B4O7. The emission intensity has been found to increase approximately 1.5 times using NaCl and 2.5 times for Na2B4O7 in Eu3+ doped CAZ phosphor as compared to the phosphor without any flux. The emission spectrum of optimized Eu3+ doped CAZ phosphor added with Na2B4O7 flux has been compared with the commercial Y2O3: Eu3+ phosphor. The CIE chromaticity coordinates and color purity calculated for Na2B4O7 in Eu3+ doped CAZ phosphor is close to commercial red phosphor. The decay curves show bi-exponential behaviour with experimental lifetimes in the range of microseconds for the as-prepared phosphors. All these results indicate that the Na2B4O7 flux assisted Eu3+ doped CAZ phosphor can serve as an efficient red phosphor under blue light for applications in white light emitting devices.