Ca9Al(PO4)7:Tb3+—crystal configuration and judd–ofelt modelling of green emanating nanophosphor

An energy-efficient, cost-effective, versatile, and eco-friendly solution combustion scheme was adopted for preparing a series of down-converted Ca9Al(PO4)7:xTb3+ (x = 10–80 mol%) nanoparticles with green emanation. Ca9Al0.40Tb0.60(PO4)7 phosphor was subjected to phase purity and crystallographic analysis using the XRD-based Rietveld refinement technique, which revealed trigonal crystallization with R3c(161) phase group. The synthesized samples underwent EDX and TEM analysis for the elemental composition and morphological behavior. The optical energy band gaps for the host (Ca9Al(PO4)7) and the optimized matrix (Ca9Al0.40Tb0.60(PO4)7) were obtained from diffuse reflectance spectral studies as 4.37 eV and 4.28 eV, respectively. UV light can effectively stimulate the nanocrystalline phosphor, resulting in substantial luminous attributes credited to 5D4 → 7FJ (J = 6,5,4,3) radiative relaxation. The PL decay curves were regressed into a mono-exponential decay function. The Auzel Model determined the radiative lifetime, non-radiative rates, and quantum efficiency for the best sample as 0.255 ms, 1572.94 s−1, and 0.714, respectively. The electric-dipole radiative probabilities of transition (derived from overall radiative rates, which include magnetic and electric-dipole) were utilized to compute the intensity parameters Ωλ (λ = 2,4,6) = 32.68 × 10−20, 9.78 × 10−20 & 22.49 × 10−20 cm2 of Tb3+ ions in Ca9Al(PO4)7 host lattice. Advanced photometric properties such as CIE coordinates (0.253, 0.558) and CCT (7136 K) further supported green glow asserting a brilliant cool green-emitting contender for manufacturing WLEDs and photonic applications.