• POONAM DEVI

      Articles written in Bulletin of Materials Science

    • Exploring the orange–red emission from novel vanadate-based nanomaterials for highly innovative photonic applications

      POONAM DEVI PRIYANKA SEHRAWAT HINA DALAL MONIKA SHEORAN NEERAJ SEHRAWAT RAJNI DUA R K MALIK

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      A homogenous crystalline Ca$_9$Y(VO$_4$)$_7$:Sm$^{3+}$ nanocrystals emanating reddish-orange light were fabricated via a simple, energy and time-saving solution combustion procedure. Structural examination revealed the trigonal symmetry with the space group R3c(161). Rietveld refinement procedure was adapted to calculate the lattice parameters and refinement factors. Morphological investigations revealed the agglomerated particles in the nano-range. The optical analysis examined a resolved emission peak at 603 nm via ${}^5$G$_{5/2}$ ${\rightarrow}$ ${}^6$H$_{7/2}$ transition, and $E_g$ (bandgap) values for Ca$_9$Y(VO$_4$)$_7$ (3.74 eV) and Ca$_9$Y$_{0.9}$Sm$_{0.1}$(VO$_4$)$_7$ (3.71 eV) were calculated from DR (diffuse reflectance) spectrum. Furthermore, the colour coordinates (0.5572, 0.3903), radiative lifetime (1.15 ms), quantum efficiency (58.4%) and colour purity (79.49%) were also evaluated in detail. These remarkable results proved the applicability of the targeted nanophosphors for constructing white LEDs, and various other photonic applications.

    • Photoluminescence dynamics and structural characteristics of green-glimmering vanadate-based nanophosphors for progressive optoelectronic applications

      HINA DALAL MUKESH KUMAR SUMAN DEVI PRIYANKA SEHRAWAT MONIKA SHEORAN POONAM DEVI NEERAJ SEHRAWAT R K MALIK

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      Fair green emission is observed in the Er$^{3+}$ activated Ca$_9$Bi(VO$_4$)$_7$ nanocrystalline material series fabricated via solution combustion methodology. A crystal prototype of the trigonal phase with R3c (161) space group having irregularly shaped grains with sizes between 43 and 61 nm is formed. Morphological aspects are examined via scanning and transmission electron microscopy (SEM and TEM). On near-UV excitation, the photoluminescence spectrum presents a good green emission at 18182 cm$^{-1}$ wavenumbers consistent with the electronic transition ${}^4$S$_{3/2}$${\rightarrow}$${}^4$I$_{15/2}$. The energy transfer phenomena are also discussed. The highest luminous intensity is observed for 8.0 mol% of Er$^{3+}$ composition (synthesized via solution combustion technique) with 382 nm excitation. d–q Exchanges authorized the presence of the concentration quenching phenomenon. Time decay analysis and non-radiative energy transfer mechanisms were also explored. Diffuse reflectance spectroscopy was taken into use to explore the energy bandgap, which lies in the semiconductor domain. The CIE coordinates lay in the greenish zone of the chromaticity plan, thus confirming their latent contention in pc-WLEDs and other innovative optoelectronic claims.

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