Characteristics of down conversion green emitting Ba3Bi2(PO4)4:Tb3+ nanosized particles for advanced illuminating devices
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Nano-scaled green-emitting Ba3Bi2(PO4)4:Tb3+ crystalline series was effectively obtained via very efficient and straightforward combustion-synthesis route for the very first time. The JCPDS data (Card No: 780204) of Ba3Bi2(PO4)4 crystal were used for profiling the diffraction patterns of various mol% samples. The structure and lattice parameters of Ba3Bi1.70Tb0.30(PO4)4 system have been investigated by Rietveld refinement analysis. Further, it was found that incorporation of dopant (Tb3+) ion into the monoclinic crystal lattice of C12/c1 (15) space group symmetry did not induce any major structural changes. Lowering in the optical band-gap value from 4.16 to 4.02 eV was observed when Ba3Bi2(PO4)4 host lattice is doped with 15 mol% of activator ions. The photoluminescence analysis of Ba3Bi2(PO4)4:Tb3+ series at 368 nm excitation yielded the bright green emission due to the 5D4 → 7F5 transition. A maximum in emission intensity is observed corresponding to the Ba3Bi1.70Tb0.30(PO4)4 composition. Critical energy distance (13.235 Å) proposed the existence of energy transfer through multipolar interaction (dipole–dipole) phenomenon, which is cross-verified by Huang analysis (s = 4.94). The value of radiative-lifetime and non-radiative transition rate are calculated to be 2.22 ms and 10.3 s−1, respectively. Furthermore, the very high value of quantum efficiency (97%) and the results of various optical analysis favor the practical utility of down-conversion Ba3Bi1.70Tb0.30(PO4)4 nanophosphor for solid-state and other illuminating devices.
The author (Ms. Jyoti Dalal) acknowledges the “Council of Scientific and Industrial Research” (CSIR), New Delhi, India for providing the economic support to the present work in the form of senior research fellowship (SRF, Award No: 09/382(0180)/2016-EMR-I).
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