Abstract
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 Ω2 higher than Ω4 of Eu3+ in the CYPO of 5D0→7F2 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 (Δλeff), fluorescence branching ratios (β) and stimulated emission cross-section (δem) 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 5D0 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: xEu3+ nanophosphors makes them capable aspirants for WLEDs using near ultra-violet excitation, solid-state laser and display systems.