Spectroscopic characteristics of Eu3+-activated Ca9Y(PO4)(7) nanophosphors in Judd-Ofelt framework

摘要

The spectroscopic properties of bright red-emitting Eu3+-doped Ca9Y(PO4)(7) (x = 0.01-1.00 mol) nanophosphors synthesized by the time-saving combustion approach were investigated by employing Judd-Ofelt theory. The band-gap analysis for the pure host was executed utilizing the Kubelka-Munk function. Scheming of Judd-Ofelt parameter was done for the first time in CYPO: Eu3+ system. The value of Omega(2) higher than Omega(4) of Eu3+ in the CYPO of D-5(0)-> F-7(2) transition leads to the red luminescence of the nanophosphors revealing the local surrounding and high covalency of the Eu3+ ions in a matrix. The other radiative parameters, such as effective bandwidth (Delta lambda(eff)), fluorescence branching ratios (beta) and stimulated emission cross-section (delta em) of the characteristic transitions have been calculated from emission spectra. The luminescence decay profiles are found to be triple-exponential in nature and in good agreement to the outcomes of the Rietveld analysis, i.e. presence of three non-centrosymmetric sites acquired by the Eu3+ ions. Auzel's model was employed to find the intrinsic radiative transition lifetime of D-5(0) level (t = 0.819 ms). The sharp red-emission with high color purity and quantum yield efficiency up to 91.7% of Ca9Y1-x(PO4)(3): xEu(3+) nanophosphors makes them capable aspirants for WLEDs using near ultra-violet excitation, solid-state laser and display systems.