Solid - State Synthesis Approach and Optical study of New Red Emitting Phosphors Li3BaSrxCa(1- x)Eu2.7Gd0.3(MoO4 )8 for White LEDs

Abstract

Solid-state synthesis methods were used for the synthesis of pure red emissive Li3BaSrxCa(1- x)Eu2.7Gd0.3 (MoO4 )8 (x = 0.0 to 1.0) phosphors, XRD, SEM, and FTIR spectra were used to characterize the materials, and their optical properties were thoroughly investigated. PL studies were examined at different excitation 275nm, 465nm, and 395 nm. All the spectra show similar emissions with the highest transition at 616 nm due to ED transition. The given phosphor Li3BaSr0.25 Ca0.75Eu2.7Gd0.3 (MoO4 )8 shows the highest intensity and is thus chosen for the temperature-dependent and Quantum yield study. According to the PL investigation, the phosphor-containing Eu3+ emits red light due to the ( 5D0 → 7F2 ) transition. The excitation spectra analysis shows that all of the phosphors exhibited broad absorption due to the charge transfer band, O2- →Mo6+ , O2- →Eu3+ transition, as well as narrow absorption bands due to the Eu3+ ion's 4f-4f electronic transition. Excitation spectra show Charge transfer band at 275 nm shows the highest intensity. The high intense band in the spectra refers to Eu3+ ions occupying the lattice's non-centrosymmetric location. All the compositions are synthesized into monoclinic crystal structures with space group C2/c and match with reference powder patterns. The thermal stability of the Li3BaSr0.25Ca0.75Eu2.7Gd0.3 (MoO4 )8 phosphor was investigated at (300 k- 500 K) as well as at low temperature from (77 K to 275 K) to be utilized for red and white LED fabrication. Quantum Yeild of the phosphor was measured and found to be 49.80% at 465 nm.