Browsing by Author "Mwankemwa, Benard"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Influence of Bi+ ions on photoluminescence properties of Tm2O3 doped borotellurite glasses for the near-infrared emission applications
    (Elsevier, 2022) Elias, Abely M.; Mwanga, Stanley Ferdinand; Mwankemwa, Benard; Anjaiah, J; Laxmikanth, C
    This paper reports the influence of bismuth ions (Bi+) on photoluminescence properties of Tm2O3 doped borotellurite based glasses (BTGS) with the composition (64-y)B2O3–30TeO2 – 5NaF- yBi2O3–1Tm2O3, where y = 0, 4, 8, 12 and 16 wt% for the near-infrared (NIR) emission applications. All glasses were prepared using the melt-quenching method and confirmed to exhibit amorphous nature by the X-ray diffraction (XRD) technique. The absorption spectra in the wavelength range of 300–2100 nm and emission spectra in the wavelength range of 400–2200 nm were studied. Increase of y wt. % value increases the 3H4→3F4 and 3F4→3H6 (near-infrared, NIR emission) intensities due to cross-relaxation (CR) and enhanced energy transfer processes between the active centres (Bi+ and Tm3+ ions), which are strongly influenced by bismuth content (Bi+) in the glass matrix. Based on Judd-Ofelt theory, the intensity parameters Ω2, Ω4 and Ω6 for each glass were determined and found to follow the trend Ω2>Ω4>Ω6 similar to the recently reported photonic glasses. Using the Ωλ parameters and reduced matrix elements, the calculation for the emission transition probability (A), radiative lifetime (τR), branching ratio (βR) and emission-cross sections ( ) of 3H4, 3H5, and 3F4 energy levels were done and found to be slightly higher than fluoride and other oxide-based glasses because of the high density and refractive index values of the present samples.
  • Thumbnail Image
    Item
    Influence of rare-earth ion doping on dielectric properties of lithium zinc borate glasses
    (Elsevier, 2022) Anjaiah, J.; Laxmikanth, C.; Mwanga, Stanley Ferdinand; Raju, P.; Shankar, J.; Rani, G. Neeraja; Mwankemwa, Benard; Ali, S, K. M.
    The dielectric constant (ε′), loss factor (tanδ), and ac conductivity (σac) of 30 Li2O-10 ZnO-(60-x) B2O3: xLn2O3, where (x = 0 and 1) and (Ln = Pr, Nd, Sm, and Eu) were investigated using a frequency range of 102–105 Hz and temperature ranging from 30 to 250 °C in this work. Differential Scanning Calorimetry (DSC) technique was employed to confirm the glassy nature of the materials under study. The dielectric parameters ε′, tanδ, and σac rise when rare-earth ions are added to the glass matrix at any frequency or temperature. Dielectric breakdown and activation energies are lower in doped than in undoped glasses while ac current flows through them at room temperature. Rare-earth ion doping's dielectric parameter values decrease with temperature as atomic number (Z) rises. The dielectric parameter values for the Pr3+ doped glass matrix are the highest. QM tunnelling model was used to describe the ac conduction behaviour of these glasses.